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Classifications

Harrison's Part

ICIMD (Inherited Metabolic Disorders)

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Inheritance

1

Autosomal Dominant HP:0000006

A single pathogenic LDLR allele is sufficient to raise LDL cholesterol from birth, and transmission is autosomal dominant. Penetrance for the biochemical phenotype is essentially complete; penetrance for clinical cardiovascular events is age-dependent and modified by treatment, Lp(a), and conventional risk factors, so expressivity is variable. The trait is more precisely co-dominant than dominant, because two pathogenic alleles produce a substantially more severe phenotype than one - the gene-dosage relation curated under has_subtypes on the umbrella entry.

Autosomal dominant inheritance Penetrance: COMPLETE Expressivity: VARIABLE

Show evidence (3 references)

PMID:24404629 SUPPORT Human Clinical

"APOB-, LDLR-, and PCSK9-related FH are inherited in an autosomal dominant manner."

GeneReviews states the mode of inheritance for LDLR-related FH explicitly.

PMID:24404629 SUPPORT Human Clinical

"Each child of an individual with a heterozygous pathogenic variant in APOB, LDLR, or PCSK9 has a 50% chance of inheriting the pathogenic variant and having FH."

States the 50% transmission risk used in genetic counselling.

PMID:1301956 SUPPORT Human Clinical

"Mutations disrupting the function of this receptor produce autosomal dominant familial hypercholesterolemia (FH)."

The founding molecular-genetic account of the disease attributes dominant FH to LDLR mutation.

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Discussions and Knowledge Gaps

2

What residual LDL receptor activity threshold actually separates patients who will respond to receptor-directed therapy from those who will not; is that threshold the same for statins as for PCSK9-directed agents; and do statins in fact lose effect in receptor-negative disease at all, given that this has never been tested against an untreated null-genotype stratum?

KNOWLEDGE GAP residual_ldlr_activity_response_threshold

Attached to

pathophysiology#Reduced Functional Hepatic LDL Receptor Activity

The entry curates residual receptor activity as the quantity that gates receptor-dependent LDL lowering, and the direction of that relation is well evidenced. The threshold is not. "Null" has been defined at under 2% of wild-type activity in functional-assay literature and operationalized as high as 15% in trial protocols, and the pivotal genotype-stratified observation rests on two receptor-negative patients. Nor is it established that statins (which act transcriptionally, on synthesis) and PCSK9-directed agents (which act post-translationally, on degradation and recycling) share a threshold - a class 1 null allele leaves nothing for either to act on, but a class 5 recycling-defective allele might respond differently to the two mechanisms. The asymmetry is sharper than that: the only genotype-stratified test in this entry is of a PCSK9 antibody, and its two receptor-negative patients were already on stable statin therapy at enrolment, so statins have never been shown here to fail in receptor-negative disease - and the entry's own cited mechanistic review reports statins helping both homozygous and heterozygous patients. The null-genotype ceiling for statins is therefore inferred from mechanism rather than demonstrated. Without a threshold, and without a drug-class-specific test, the relation informs reasoning but does not yet support a decision rule.

Proposed experiments

Prospective genotype-stratified response study with quantified residual receptor activity

residual_activity_response_threshold_study

In a homozygous and compound-heterozygous FH cohort, measure residual LDLR activity for each proband's allele pair in a standardized cell-based uptake assay, then relate that quantity to the achieved LDL-C reduction on a high-intensity statin and, separately, on a PCSK9 monoclonal antibody. The readout is whether a single activity threshold predicts response for both drug classes or whether the classes have different thresholds.

Does the arterial disease of any available LDLR-deficient animal model reproduce the human course closely enough to test interventions aimed at events rather than at LDL levels?

HUMAN MODEL MISMATCH ldlr_model_arterial_translation

Attached to

pathophysiology#Premature Atherosclerotic Cardiovascular Events

The clearance defect translates cleanly across species - the Ldlr-/- mouse reproduces it and adenoviral receptor restoration reverses it - but the arterial arm does not. Murine lipoprotein metabolism is apoB48- and HDL-dominated, so the mouse does not reach human homozygous-FH cholesterol levels and develops limited spontaneous atherosclerosis on chow. The WHHL rabbit is far closer in lipoprotein physiology and does develop coronary disease, but the strain history reports that lesion rupture there requires secondary mechanical forces such as spasm, so it is not a clean analogue of spontaneous human plaque rupture. The genome-edited LDLR-knockout cynomolgus monkey reaches human-like lipid levels and develops xanthoma within a year, but the published cohort is six founder animals with short follow-up and possible editing mosaicism. Each model is informative for the node it was curated against and none is currently adequate for event-endpoint intervention studies.

Proposed experiments

Cross-species comparison of plaque composition and rupture triggers under matched cumulative LDL exposure

cross_species_plaque_rupture_comparison

Compare coronary and aortic lesion composition, fibrous cap thickness, and spontaneous versus provoked rupture between LDLR-deficient rabbits, LDLR-knockout primates, and human FH imaging cohorts matched on cumulative LDL-C exposure rather than on age, to establish which model, if any, supports event-level extrapolation.

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Pathophysiology

14

LDLR Loss-of-Function Variant

A germline pathogenic variant in LDLR at 19p13.2. The gene spans more than 45 kb in 18 exons whose boundaries map onto the receptor's functional modules - the cysteine-rich ligand-binding repeats, the EGF-precursor homology domain, the O-linked sugar domain, the transmembrane segment and the cytoplasmic tail - so the mutated exon largely predicts which step of the receptor's itinerary is broken. More than 2300 unique FH-associated LDLR variants have been catalogued, spanning missense, nonsense, frameshift, splice, promoter and exon-level copy-number changes. This node is the single lesion; the five nodes immediately downstream are the alternative steps at which it can act.

LDLR hgnc:6547

Genetic context LDLR hgnc:6547 variant_origin: GERMLINE functional_impact_category: LOSS_OF_FUNCTION

The variant consequence is loss of function - fewer functional LDL receptors reach or persist on the hepatocyte surface. Recorded on the genetic context rather than as a Descriptor modifier because the claim is about the consequence of an allele. The severity of that loss is allele-specific and is the subject of the class nodes downstream.

low-density lipoprotein particle receptor activity GO:0005041 ↓ DECREASED

liver UBERON:0002107

Downstream

Absent LDL Receptor Synthesis Null (class 1) alleles - large deletions removing the promoter, nonsense and frameshift changes, and alleles producing no detectable protein - abolish receptor synthesis outright.

Impaired ER-to-Golgi Transport of the LDL Receptor Class 2 alleles allow synthesis but the receptor misfolds and is retained in the endoplasmic reticulum instead of maturing through the Golgi.

Defective LDL Binding at the Hepatocyte Surface Class 3 alleles produce a receptor that reaches the surface but binds apoB-100 poorly, typically through changes in the cysteine-rich ligand-binding repeats or in the EGF-precursor domain that positions them.

Defective Clustering in Clathrin-Coated Pits Class 4 alleles disable the cytoplasmic internalization signal, so a fully synthesized, surface-expressed, ligand-competent receptor never enters the cell.

Defective Endosomal Ligand Release and Receptor Recycling Class 5 alleles allow binding and internalization but the receptor fails to release LDL in the acidified endosome, so receptor and ligand are degraded together instead of the receptor returning to the surface.

Show evidence (3 references)

PMID:1301956 SUPPORT Human Clinical

"Mutations disrupting the function of this receptor produce autosomal dominant familial hypercholesterolemia (FH)."

States the causal relation that defines this entry's trigger node.

PMID:2988123 SUPPORT In Vitro

"This gene is more than 45 kilobases in length and contains 18 exons, most of which correlate with functional domains previously defined at the protein level."

Establishes the exon-to-domain correspondence that underlies the structure-function mapping used by the class nodes downstream.

PMID:34906454 SUPPORT Human Clinical

"In this study, we provide consensus recommendations for the most common FH-associated gene, LDLR, where >2300 unique FH-associated variants have been identified."

Quantifies the size of the LDLR allelic series curated by this entry.

Absent LDL Receptor Synthesis

The class 1 (null, receptor-negative) branch. No immunodetectable LDL receptor protein is made, because the allele deletes the promoter, produces no mRNA, or produces mRNA that yields no protein. This is the most severe branch and the one with the least therapeutic room: there is no receptor to upregulate. In clinical trials of homozygous disease it is operationalized as "null-null" or receptor-negative status.

hepatocyte CL:0000182

low-density lipoprotein particle receptor activity GO:0005041 ∅ ABSENT

Downstream

Reduced Functional Hepatic LDL Receptor Activity Absent receptor protein is the limiting case of reduced receptor activity.

Show evidence (2 references)

PMID:3343347 SUPPORT In Vitro

"Four of the alleles produced no mRNA. Three of these four mRNA- alleles had large deletions ranging from 6 to 20 kb that eliminated the promoter region of the gene."

Documents the molecular routes to complete absence of receptor protein.

PMID:32813947 SUPPORT Human Clinical

"This disorder is associated with genetic variants that result in virtually absent (null-null) or impaired (non-null) LDL-receptor activity."

Shows the null versus non-null distinction being used as a formal stratifier in a contemporary phase 3 trial.

Impaired ER-to-Golgi Transport of the LDL Receptor

The class 2 (transport-defective) branch. The receptor is synthesized but misfolds and is retained in the endoplasmic reticulum rather than being further glycosylated in the Golgi and delivered to the surface. Retention may be complete (class 2a) or partial (class 2b), and partial retention leaves residual surface receptor - which matters therapeutically, because residual receptor is what receptor-directed drugs act on.

hepatocyte CL:0000182

endoplasmic reticulum to Golgi vesicle-mediated transport GO:0006888 ↓ DECREASED

Downstream

Reduced Functional Hepatic LDL Receptor Activity A receptor stuck in the ER never reaches the surface, so it contributes nothing to LDL clearance regardless of whether its ligand-binding sequence is intact.

Show evidence (2 references)

PMID:32015373 SUPPORT In Vitro

"Of the analysed variants, we found six non-pathogenic LDLR variants and ten pathogenic variants distributed as follow: three class 3 variants; four class 2 variants; and three class 5 variants."

Assigns patient variants to the transport-defective class by functional assay.

PMID:25386756 SUPPORT In Vitro

"Additionally confocal microscopy allowed the assignment of different class mutation to the variants assayed."

Confirms that subcellular localization imaging is what distinguishes an ER-retained receptor from a surface-expressed one.

Defective LDL Binding at the Hepatocyte Surface

The class 3 (binding-defective) branch. Receptor reaches the surface in normal numbers but binds apoB-100-containing LDL with reduced affinity. Changes typically fall in the cysteine-rich ligand-binding repeats or in the EGF-precursor homology domain that holds them in a binding-competent conformation. This is the receptor-side mirror of the ligand-side defect curated in Familial_Defective_Apolipoprotein_B-100 - the same handshake fails, from the other side.

hepatocyte CL:0000182

LDLR hgnc:6547

low-density lipoprotein particle binding GO:0030169 ↓ DECREASED

Downstream

Reduced Functional Hepatic LDL Receptor Activity A surface receptor that cannot capture its ligand removes no LDL, so functional receptor activity falls even though receptor abundance is normal.

Show evidence (2 references)

PMID:32015373 SUPPORT In Vitro

"They showed similar expression to wt LDLR but demonstrated deficient LDL binding."

The defining functional signature of the class 3 branch: receptor is expressed at normal levels yet binds LDL poorly, separating a binding defect from a synthesis or trafficking defect.

PMID:31106925 SUPPORT In Vitro

"All new LDLR variants found in our patients were functionally validated in CHO-ldlA7 cells. The LDLR activity was measured by flow cytometry and LDLR expression was detected by immunofluorescence."

Describes the paired activity/expression measurement that identifies a binding defect - normal expression with reduced activity.

Defective Clustering in Clathrin-Coated Pits

The class 4 (internalization-defective) branch. The cytoplasmic tail of the LDL receptor carries the signal that concentrates it in clathrin-coated pits; a change there leaves a receptor that is expressed and binds LDL normally but is distributed diffusely over the surface and enters the cell slowly. The founding example is patient J.D., whose receptor carries a tyrosine-to-cysteine substitution at residue 807. Because the LDLRAP1/ARH adaptor serves this same step, the recessive LDLRAP1 disease is the phenocopy of this branch acting in trans.

hepatocyte CL:0000182

clathrin-dependent endocytosis GO:0072583 ↓ DECREASED

Experimental models

J.D. fibroblast strain (internalization-defective LDLR alleles) PRIMARY CELL CULTURE The founding measurement of this node. Binding and internalization are assayed separately in the same cells, so the defect is localized to the internalization step rather than inferred from a lowered uptake total.

Downstream

Reduced Functional Hepatic LDL Receptor Activity A receptor that binds LDL but does not internalize it does not clear it; the bound particle is not delivered to the lysosome.

Show evidence (2 references)

PMID:3955657 SUPPORT In Vitro

"Upon transfection into receptor-deficient hamster cells, the cDNA specified a receptor that bound LDL normally, but entered the cell slowly."

Separates binding from internalization experimentally - the defining observation for this class.

PMID:3955657 SUPPORT In Vitro

"Electron microscopy showed that this receptor was distributed diffusely over the cell surface, whereas the receptor produced by the normal cDNA was concentrated in coated pits."

Direct morphological evidence that the lesion is failure to cluster in clathrin-coated pits.

Defective Endosomal Ligand Release and Receptor Recycling

The class 5 (recycling-defective) branch. Binding and internalization are intact, but the receptor fails to release LDL when the endosome acidifies, so receptor and ligand traffic together to the lysosome and the receptor is consumed rather than returned to the surface. Each receptor therefore makes one round trip instead of many, and functional clearance capacity collapses even though synthesis is normal. This is also the step that PCSK9 subverts pharmacologically, which is why PCSK9-directed drugs raise receptor abundance in patients who still have recyclable receptor.

hepatocyte CL:0000182

receptor recycling GO:0001881 ↓ DECREASED

Downstream

Reduced Functional Hepatic LDL Receptor Activity Loss of recycling converts a reusable receptor into a single-use one, cutting the LDL particles cleared per receptor synthesized.

Show evidence (2 references)

PMID:32015373 SUPPORT In Vitro

"LDLR structure is organized in 5 different domains, including an EGF-precursor homology domain that plays a pivotal role in lipoprotein release and receptor recycling."

Localizes ligand release and recycling to a specific receptor domain.

PMID:32015373 SUPPORT In Vitro

"In this way, although the protein structure is not affected in LDLR expression or LDL binding and uptake activities, the alteration introduced by the asparagine is enough to cause a defect in recycling of the protein."

Isolates the class 5 defect: expression, binding and uptake are all intact and recycling alone fails, which is what distinguishes this branch from the synthesis, trafficking and binding branches.

Reduced Functional Hepatic LDL Receptor Activity

The convergence node of the allelic series. Whichever step is broken - synthesis, ER export, ligand binding, internalization, or recycling - the measurable output is the same: fewer LDL particles cleared per unit time by the hepatocyte. Functional assays report this as a single quantity (percentage of wild-type LDL uptake), which is why class assignment and residual activity are recorded separately: the class says *where* the itinerary breaks, the residual activity says *how much* capacity survives. Null alleles are conventionally under about 2% of normal activity, though trial protocols have operationalized "null" at thresholds as high as 15%.

hepatocyte CL:0000182

receptor-mediated endocytosis GO:0006898 ↓ DECREASED

low-density lipoprotein particle receptor activity GO:0005041 ↓ DECREASED

liver UBERON:0002107

Experimental models

CHO-ldlA7 heterologous LDLR variant expression assay CELL LINE Quantifies the residual activity a given LDLR allele supports, resolved into the three separable steps - surface expression, binding, uptake - that distinguish the receptor classes from one another.

Activity-normalized prime editing saturation screen of LDLR coding variants CELL LINE Measures residual LDL uptake for each of 5,184 coding variants, turning the receptor-activity axis this node represents into a per-allele quantity that separates known pathogenic from known benign variants and tracks LDL-C in an independent human cohort.

Animal models

Ldlr-knockout mouse Mouse rescues Restoring hepatic LDL receptor expression by adenoviral delivery normalized the elevated IDL/LDL within four days, demonstrating that the receptor deficit is both necessary and sufficient for the phenotype in this model.

Downstream

Impaired Receptor-Mediated Clearance of Plasma LDL Hepatic LDL receptors perform most clearance of circulating LDL, so a fall in functional receptor activity directly lengthens LDL residence time in plasma.

Residual Receptor Activity Gates Receptor-Dependent LDL Lowering The same residual activity that sets the untreated LDL level also sets how much a receptor-directed drug can achieve, because those drugs act by increasing the number of functional receptors rather than by creating them.

Show evidence (2 references)

PMID:1301956 SUPPORT Human Clinical

"The low density lipoprotein (LDL) receptor is a cell surface transmembrane protein that mediates the uptake and lysosomal degradation of plasma LDL, thereby providing cholesterol to cells."

States the receptor function whose reduction this node represents.

PMID:32015373 SUPPORT In Vitro

"These results can be incorporated into clinical management of patients by helping guide the appropriate level of treatment intensity depending on the extent of loss of LDLR activity."

Treats residual LDLR activity as the single clinically actionable output of the allelic series.

Residual Receptor Activity Gates Receptor-Dependent LDL Lowering

The pharmacogenetic node, and the reason the allelic series is clinically actionable rather than merely descriptive. Statins lower intracellular cholesterol and thereby induce more LDL receptor; PCSK9 antibodies and inclisiran prevent or reduce PCSK9-mediated receptor degradation. Both families of drugs work by putting *more* receptor on the hepatocyte surface, so both require a receptor that can be made and can function. The genotype-stratified evidence below is for a PCSK9 antibody: in the two receptor-negative (null-null) homozygotes studied there was nothing to induce and the response was absent, while in receptor-defective homozygotes there was residual receptor and the response was preserved. Whether statins behave the same way in receptor-negative disease has not been tested here - the two null patients in that trial were already on stable statin therapy at enrolment - and the mechanisms differ (statins act transcriptionally on receptor synthesis, PCSK9-directed agents post-translationally on receptor degradation and recycling), so the statin/PCSK9 asymmetry is carried as an open question in the residual_ldlr_activity_response_threshold discussion rather than asserted. LDLR-independent agents - the MTP inhibitor lomitapide, the ANGPTL3 antibody evinacumab, and lipoprotein apheresis - bypass the receptor entirely and retain effect in null-null disease. This node is the target of the treatment entries curated below.

hepatocyte CL:0000182

liver UBERON:0002107

Experimental models

JD iPSC-derived hepatocyte-like cells IPSC DERIVED MODEL Control hepatocyte-like cells raise LDL uptake when given lovastatin and the FH cells do not. The block is not in the drug's proximal action: the same study reports that FH cells induce LDLR mRNA on lovastatin to a similar extent as controls. What the genotype bounds is the usefulness of that induction, because the additional receptor it produces is the defective receptor. That is the gating relation observed at the level of the hepatocyte itself.

Animal models

LDLR-knockout cynomolgus monkey Cynomolgus monkey recapitulates Complete receptor knockout reproduces the drug-refractory phenotype that defines receptor-negative homozygous disease.

Show evidence (3 references)

PMID:24014831 SUPPORT Human Clinical

"No reduction was seen in the 2 receptor-negative patients."

The negative half of the relation - a receptor-directed drug does nothing when no receptor can be made.

PMID:24014831 SUPPORT Human Clinical

"Over the treatment periods, mean±SD LDL cholesterol reductions in the 6 LDL receptor-defective patients were 19.3±16% and 26.3±20% with 4- and 2-week dosing, respectively"

The positive half - the same drug in the same trial lowers LDL when residual receptor activity exists.

PMID:32813947 SUPPORT Human Clinical

"The LDL cholesterol level was lower in the evinacumab group than in the placebo group in patients with null-null variants (-43.4% vs. +16.2%) and in those with non-null variants (-49.1% vs. -3.8%)."

Shows the complementary case - an LDLR-independent mechanism works in both genotype strata, which is what makes the gating relation therapeutically consequential rather than merely prognostic.

Impaired Receptor-Mediated Clearance of Plasma LDL

Reduced hepatic receptor capacity lengthens the residence time of apoB-100-containing LDL and IDL in plasma. The defect is specific to the receptor's ligands: HDL clearance is unaffected, which is why the biochemical phenotype is an isolated elevation of LDL rather than a generalized dyslipidemia.

low-density lipoprotein particle clearance GO:0034383 ↓ DECREASED

liver UBERON:0002107

Experimental models

JD iPSC-derived hepatocyte-like cells IPSC DERIVED MODEL Patient-genotype hepatocyte-like cells are deficient in LDL-C uptake relative to controls, the cellular counterpart of the plasma clearance defect this node asserts.

Animal models

Ldlr-knockout mouse Mouse recapitulates Directly measures the clearance defect that this node represents, in the cleanest possible genetic background - complete receptor absence.

Downstream

Lifelong Elevation of Plasma LDL Cholesterol Reduced clearance against unchanged production raises the steady-state plasma LDL concentration, from birth and for life.

Show evidence (2 references)

PMID:8183926 SUPPORT Model Organism

"LDLR(-/-) mice had a relatively isolated elevation in plasma LDL"

Shows that loss of the receptor produces a selective LDL clearance defect rather than a global lipoprotein abnormality.

PMID:8349823 SUPPORT Model Organism

"We conclude that the LDL receptor is responsible in part for the low levels of VLDL, IDL, and LDL in wild-type mice"

Attributes normal plasma LDL levels to receptor-mediated clearance.

Lifelong Elevation of Plasma LDL Cholesterol

The defining biochemical phenotype. Because the receptor defect is constitutional, LDL cholesterol is elevated from birth, so the arterial tree accumulates cholesterol exposure over decades rather than from midlife onward. Untreated heterozygotes typically exceed 190 mg/dL; biallelic disease often exceeds 400-500 mg/dL.

Downstream

Endothelial Dysfunction and Subendothelial LDL Retention Sustained high plasma LDL drives entry of apoB particles into the arterial intima and their retention on subendothelial proteoglycan - the initiating step of the shared atherogenesis programme.

Extravascular Cholesterol Deposition in Tendon, Skin, and Cornea The same circulating excess deposits outside the arterial wall, producing the classical stigmata. These are specific but insensitive, and are less often seen now that treatment begins earlier.

Show evidence (2 references)

PMID:24404629 SUPPORT Human Clinical

"A clinical diagnosis of FH can be established in a proband with characteristic clinical features and significantly elevated LDL-C levels (typically >190 mg/dL in adults and >160 mg/dL in children)."

Gives the diagnostic LDL-C thresholds for the untreated phenotype.

PMID:37130090 SUPPORT Human Clinical

"a low-density lipoprotein cholesterol (LDL-C) >10 mmol/L (>400 mg/dL) is suggestive of HoFH and warrants further evaluation"

Gives the biallelic-disease threshold used in current consensus guidance.

Endothelial Dysfunction and Subendothelial LDL Retention

Conformance node. The atherogenic cascade downstream of the LDL elevation is the conserved one modelled in the atherogenesis module and is not re-derived here; what is disease-specific is that the apoB-lipoprotein driver is present from birth and at several times the usual concentration, so the same programme runs decades earlier.

endothelial cell of artery CL:1000413

artery UBERON:0001637

Animal models

Watanabe heritable hyperlipidemic (WHHL) rabbit Rabbit recapitulates Spontaneous, diet-independent hypercholesterolemia from receptor deficiency drives the initiating arterial events - oxidized LDL accumulation, endothelial adhesion molecule expression, and monocyte infiltration.

Downstream

Monocyte Recruitment and Macrophage Foam Cell Formation Retained and modified LDL recruits monocytes that become lipid-laden macrophages.

Show evidence (1 reference)

PMID:31748469 SUPPORT Model Organism

"Oxidized LDL accumulates in the arterial wall, monocyte adhesion molecules are expressed on arterial endothelial cells, and monocyte-derived macrophages infiltrate the arterial intima, resulting in the formation and progression of atherosclerosis."

Describes the initiating arterial events as established in the LDLR-deficient rabbit, the model in which they were demonstrated in vivo.

Monocyte Recruitment and Macrophage Foam Cell Formation

Conformance node. Recruited monocyte-derived macrophages take up modified LDL and become foam cells, the cellular substance of the early lesion.

macrophage CL:0000235 foam cell CL:0000891

artery UBERON:0001637

Downstream

Premature Atherosclerotic Cardiovascular Events Lesion growth, destabilization and thrombosis convert subclinical plaque into clinical events; the intervening steps are the conserved ones in the atherogenesis module.

Show evidence (1 reference)

PMID:31748469 SUPPORT Model Organism

"monocyte-derived macrophages infiltrate the arterial intima, resulting in the formation and progression of atherosclerosis"

States macrophage infiltration as the step that builds the lesion.

Premature Atherosclerotic Cardiovascular Events

Conformance node. Angina, myocardial infarction, and less often stroke, occurring decades earlier than in the general population. In biallelic disease events may occur in childhood or adolescence and are accompanied by calcific aortic valve and aortic root disease, which is a supravalvular rather than purely valvular lesion and is not prevented by LDL lowering as reliably as coronary events are.

coronary artery UBERON:0001621 aortic valve UBERON:0002137

Show evidence (2 references)

PMID:24404629 SUPPORT Human Clinical

"increases the risk of premature cardiovascular events such as angina and myocardial infarction; stroke occurs more rarely"

Names the clinical events and their relative frequency.

PMID:24404629 SUPPORT Human Clinical

"Individuals with a more severe phenotype, often as a result of biallelic variants, can present with very significant elevations in LDL-C (>500 mg/dL), early-onset coronary artery disease (CAD; presenting as early as childhood in some), and calcific aortic valve disease."

Establishes the childhood-onset and aortic valve arms in biallelic disease.

Extravascular Cholesterol Deposition in Tendon, Skin, and Cornea

Macrophage-mediated deposition of LDL-derived cholesterol outside the arterial wall, producing tendon xanthoma (Achilles and extensor tendons of the hands), xanthelasma at the eyelids, and premature corneal arcus. These signs are highly specific for the untreated phenotype and are used in the Dutch Lipid Clinic Network and Simon Broome criteria, but they are insensitive - absence does not exclude the diagnosis, and early treatment both prevents and can reverse them.

macrophage CL:0000235

tendon UBERON:0000043 cornea UBERON:0000964 eyelid UBERON:0001711

Show evidence (3 references)

PMID:24404629 SUPPORT Human Clinical

"Xanthelasmas (yellowish, waxy deposits) can occur around the eyelids."

Documents the periocular deposition site.

PMID:24404629 SUPPORT Human Clinical

"Individuals with FH may develop corneal arcus (white, gray, or blue opaque ring in the corneal margin as a result of cholesterol deposition) at a younger age than those without FH."

Documents corneal deposition and its premature timing.

PMID:37730951 SUPPORT Model Organism

"In addition, periocular xanthoma was observed only 1 year after birth."

Independent demonstration in an LDLR-knockout primate that removing the receptor alone is sufficient to produce periocular xanthoma.

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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

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Phenotypes

9

Cardiovascular 4

Premature Coronary Artery Atherosclerosis HP:0001677

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:24404629 SUPPORT Human Clinical

"Familial hypercholesterolemia (FH) is characterized by significantly elevated low-density lipoprotein cholesterol (LDL-C) that leads to atherosclerotic plaque deposition in the coronary arteries and proximal aorta at an early age"

States both the lesion and its premature timing.

Myocardial Infarction HP:0001658

Show evidence (1 reference)

PMID:24404629 SUPPORT Human Clinical

"increases the risk of premature cardiovascular events such as angina and myocardial infarction; stroke occurs more rarely"

Names myocardial infarction as a principal clinical event.

Angina Pectoris HP:0001681

Show evidence (1 reference)

PMID:24404629 SUPPORT Human Clinical

"increases the risk of premature cardiovascular events such as angina and myocardial infarction"

Names angina as a presenting cardiovascular event.

Calcific Aortic Valve Disease Aortic valve calcification HP:0004380

Show evidence (1 reference)

PMID:24404629 SUPPORT Human Clinical

"Individuals with a more severe phenotype, often as a result of biallelic variants, can present with very significant elevations in LDL-C (>500 mg/dL), early-onset coronary artery disease (CAD; presenting as early as childhood in some), and calcific aortic valve disease."

Identifies calcific aortic valve disease as a feature of severe biallelic disease.

Eye 1

Premature Corneal Arcus HP:0001084

Show evidence (1 reference)

PMID:24404629 SUPPORT Human Clinical

"Individuals with FH may develop corneal arcus (white, gray, or blue opaque ring in the corneal margin as a result of cholesterol deposition) at a younger age than those without FH."

Establishes both the sign and the premature timing that gives it diagnostic value.

Head and Neck 1

Xanthelasma HP:0001114

Show evidence (1 reference)

PMID:24404629 SUPPORT Human Clinical

"Xanthelasmas (yellowish, waxy deposits) can occur around the eyelids."

Documents the sign and its location.

Integument 1

Tendon Xanthoma Tendon xanthomatosis HP:0010874

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:24404629 SUPPORT Human Clinical

"Xanthomas (cholesterol deposits in tendons) may be visible in the Achilles tendons or tendons of the hands and worsen with age as a result of extremely high cholesterol levels."

Names the sites and the progressive course. Frequency is deliberately omitted - reported prevalence varies widely with treatment era and ascertainment, and no quotable figure specific to LDLR-related FH was available.

Metabolism 2

Hypercholesterolemia VERY_FREQUENT HP:0003124

Temporal: CHRONIC

Show evidence (2 references)

PMID:1301956 SUPPORT Human Clinical

"Affected individuals have elevated plasma levels of LDL, which causes premature coronary atherosclerosis."

States the defining biochemical abnormality of LDLR-mutation carriers.

PMID:24404629 SUPPORT Human Clinical

"Familial hypercholesterolemia (FH) is characterized by significantly elevated low-density lipoprotein cholesterol (LDL-C)"

GeneReviews states the elevation as the characterizing feature. Frequency is set VERY_FREQUENT because the biochemical phenotype is essentially fully penetrant in variant carriers.

Elevated LDL Cholesterol VERY_FREQUENT Increased LDL cholesterol concentration HP:0003141

Temporal: CHRONIC

Show evidence (2 references)

PMID:24404629 SUPPORT Human Clinical

"A clinical diagnosis of FH can be established in a proband with characteristic clinical features and significantly elevated LDL-C levels (typically >190 mg/dL in adults and >160 mg/dL in children)."

Gives the diagnostic thresholds and establishes the phenotype's universality.

PMID:37130090 SUPPORT Human Clinical

"a low-density lipoprotein cholesterol (LDL-C) >10 mmol/L (>400 mg/dL) is suggestive of HoFH and warrants further evaluation"

Gives the corresponding threshold in biallelic disease.

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Genetic Associations

1

LDLR (Pathogenic Mutations)

Gene: LDLR hgnc:6547 gene page relationship_type: CAUSATIVE variant_origin: GERMLINE

Autosomal Dominant

Show evidence (5 references)

PMID:34906454 SUPPORT Human Clinical

"In this study, we provide consensus recommendations for the most common FH-associated gene, LDLR, where >2300 unique FH-associated variants have been identified."

Establishes both LDLR primacy and the scale of the allelic series.

PMID:34906454 SUPPORT Human Clinical

"The consensus LDLR variant modifications to existing ACMG/AMP guidelines include (1) alteration of population frequency thresholds, (2) delineation of loss-of-function variant types, (3) functional study criteria specifications, (4) cosegregation criteria specifications, and (5) specific use and..."

Names the gene-specific interpretation rules that govern LDLR variant classification.

PMID:30306860 SUPPORT Human Clinical

"The most common (60-80%) FH cause is mutations of the LDL Receptor (LDLR) protein (6 classes with a different number of receptors and functionality)."

Quantifies the LDLR share of FH and names the receptor-class scheme. Note the source counts six classes; the five curated above are the classical set, with the sixth (defective basolateral targeting) omitted because no quotable functional evidence for it was found.

+ 2 more references

Variants (5)

Class 1 - null (receptor-negative) Pathogenic

null

No LDL receptor protein is synthesized. Large deletions removing the promoter, nonsense and frameshift changes, and alleles that make normal mRNA but no detectable protein. Homozygotes for two such alleles are receptor-negative and respond poorly or not at all to receptor-directed drugs.

Class 2 - transport-defective Pathogenic

missense

The receptor is synthesized but misfolds and is retained in the endoplasmic reticulum instead of maturing through the Golgi to the surface. Retention may be complete (2a) or partial (2b).

Class 3 - binding-defective Pathogenic

missense

Receptor reaches the surface but binds apoB-100 poorly. Changes fall in the cysteine-rich ligand-binding repeats or in the EGF-precursor homology domain that orients them.

Class 4 - internalization-defective Pathogenic

missense

Receptor is expressed and binds LDL normally but fails to cluster in clathrin-coated pits, because the cytoplasmic internalization signal is disrupted. The founding allele is the J.D. mutation, a tyrosine-to-cysteine substitution at residue 807.

Show evidence (1 reference)

PMID:189940 SUPPORT In Vitro

"In this unique mutant strain (derived from subject J.D.), the cell surface receptor for plasma low density lipoprotein (LDL) was able to bind 125I-labeled LDL normally, but internalization of the receptor-bound lipoprotein failed to occur."

The founding description of this class, in the strain it is named for: it establishes a profound internalization defect against preserved binding. It supports neither of the two more specific claims in the description above - the Y807C substitution and the failure to cluster in coated pits were both shown later, and both rest on PMID:3955657, cited on the corresponding pathophysiology node.

Class 5 - recycling-defective Pathogenic

missense

Receptor binds and internalizes LDL but fails to release it in the acidified endosome, so receptor and ligand are degraded together and the receptor is not returned to the surface.

💊

Medical Actions

10

Statin (HMG-CoA Reductase Inhibitor) Therapy

Action: Pharmacotherapy NCIT:C15986

Agent: statin CHEBI:87631

Platform: Small molecule

First-line, lifelong LDL-lowering therapy. The mechanism is receptor-side and therefore genotype-sensitive: inhibiting HMG-CoA reductase lowers intracellular cholesterol, which de-represses LDLR transcription and puts more receptor on the hepatocyte surface. The drug therefore amplifies whatever receptor capacity the genotype leaves. Note that statins have not been tested against a receptor-negative genotype stratum in this entry's evidence, and the cited mechanistic review reports statins helping both homozygous and heterozygous patients, so the null-genotype ceiling is inferred from mechanism rather than demonstrated. In a 2146-patient FH cohort followed a mean 8.5 years, statin treatment reduced coronary heart disease risk by 76%.

Mechanism Target:

ACTIVATES Residual Receptor Activity Gates Receptor-Dependent LDL Lowering — Statins act by inducing residual LDL receptor, so their effect is bounded by how much functional receptor the genotype permits.

Show evidence (1 reference)

PMID:37371118 SUPPORT Other

"Statins proved to be the first blockbuster drug, helping both HoFH and HeFH individuals by inhibiting the cholesterol synthesis pathway rate-limiting enzyme HMG-CoA reductase and inducing the LDL receptor."

States the receptor-inducing mechanism that makes the effect genotype-dependent.

Show evidence (5 references)

PMID:19001495 SUPPORT Human Clinical

"We observed an overall risk reduction of 76% (hazard ratio 0.24 (95% confidence interval 0.18 to 0.30), P<0.001)."

Quantifies the cardiovascular benefit of statin therapy in an FH cohort.

PMID:24404629 SUPPORT Other

"statins can be used in children starting around age eight years"

GeneReviews sets the paediatric initiation age. The recommendation is made for FH as a class rather than for LDLR-related FH specifically.

PMID:31618540 SUPPORT Human Clinical

"initiation of statin therapy during childhood in patients with familial hypercholesterolemia slowed the progression of carotid intima-media thickness and reduced the risk of cardiovascular disease in adulthood"

Twenty-year follow-up of a childhood pravastatin trial, genetically confirmed in 98% of the 214 patients, showing that treating from childhood changes the adult arterial trajectory rather than only the lipid number. This is the outcome claim behind starting statins in childhood; the GeneReviews item above states only that it is done.

+ 2 more references

PCSK9 Monoclonal Antibody Therapy

Action: Pharmacotherapy NCIT:C15986

Agent: PCSK9 inhibitor NCIT:C190797

Platform: Monoclonal antibody

Alirocumab and evolocumab neutralize circulating PCSK9, preventing PCSK9-directed lysosomal degradation of the LDL receptor and so increasing receptor recycling and surface abundance. Like statins this is a receptor-amplifying mechanism, and the AMG 145 (evolocumab) homozygous-FH study is the cleanest published demonstration that the amplification requires a receptor to amplify: LDL cholesterol fell in receptor-defective patients and not at all in the receptor-negative ones, within the same protocol and at the same doses.

Mechanism Target:

ACTIVATES Residual Receptor Activity Gates Receptor-Dependent LDL Lowering — Blocking PCSK9 spares existing LDL receptor from degradation, raising surface receptor abundance in patients who retain functional receptor and achieving nothing in those who do not.

Show evidence (1 reference)

PMID:24014831 SUPPORT Human Clinical

"This study demonstrates significant and dose-related LDL cholesterol lowering with a PCSK9 monoclonal antibody in homozygous familial hypercholesterolemia patients with defective LDL receptor activity but no reduction in those who were receptor negative."

The genotype-stratified result that defines the boundary of this therapy.

Show evidence (2 references)

PMID:24014831 SUPPORT Human Clinical

"Over the treatment periods, mean±SD LDL cholesterol reductions in the 6 LDL receptor-defective patients were 19.3±16% and 26.3±20% with 4- and 2-week dosing, respectively"

Quantifies the response in receptor-defective homozygous disease.

PMID:37130090 SUPPORT Human Clinical

"Addition of novel, efficacious therapies (i.e. inhibitors of proprotein convertase subtilisin/kexin type 9, followed by evinacumab and/or lomitapide) offers potential to attain LDL-C goal or reduce the need for LA."

Places PCSK9 inhibition in the current consensus treatment sequence for severe disease.

Evinacumab (ANGPTL3 Inhibition)

Action: Pharmacotherapy NCIT:C15986

Agent: evinacumab NCIT:C20401

Platform: Monoclonal antibody

An angiopoietin-like 3 monoclonal antibody that lowers LDL cholesterol by a route that does not require the LDL receptor. This is the therapeutic complement of everything above: in the phase 3 homozygous-FH trial it lowered LDL cholesterol by a similar amount in patients with null-null variants and in those with non-null variants, so it is the option that remains when the receptor-directed drugs have nothing to act on.

Mechanism Target:

INHIBITS Lifelong Elevation of Plasma LDL Cholesterol — Lowers plasma LDL cholesterol without acting through the LDL receptor, so the effect is preserved regardless of receptor class.

Show evidence (1 reference)

PMID:32813947 SUPPORT Human Clinical

"The LDL cholesterol level was lower in the evinacumab group than in the placebo group in patients with null-null variants (-43.4% vs. +16.2%) and in those with non-null variants (-49.1% vs. -3.8%)."

Demonstrates genotype-independent efficacy, the defining property of this agent.

Show evidence (1 reference)

PMID:32813947 SUPPORT Human Clinical

"At week 24, patients in the evinacumab group had a relative reduction from baseline in the LDL cholesterol level of 47.1%, as compared with an increase of 1.9% in the placebo group"

Reports the primary efficacy result of the pivotal randomized trial.

Lomitapide (Microsomal Triglyceride Transfer Protein Inhibition)

Action: Pharmacotherapy NCIT:C15986

Agent: lomitapide CHEBI:72297

Platform: Small molecule

An MTP inhibitor that reduces hepatic assembly and secretion of apoB-containing lipoproteins. Like evinacumab it acts upstream of the receptor rather than through it, so it is expected to be genotype-independent - though, unlike the evinacumab trial, the pivotal lomitapide study was single-arm, open-label, and not genotype-stratified, so its 50% reduction is a whole-cohort figure and not a demonstration of effect in receptor-negative disease specifically. Hepatic steatosis, transaminase elevation, gastrointestinal intolerance, and fat-soluble vitamin depletion constrain its use and require monitoring.

Mechanism Target:

INHIBITS Lifelong Elevation of Plasma LDL Cholesterol — Reduces the production side of the LDL steady state rather than the clearance side, bypassing the receptor defect entirely.

Show evidence (1 reference)

PMID:23122768 SUPPORT Human Clinical

"LDL cholesterol was reduced by 50% (95% CI -62 to -39) from baseline"

Quantifies LDL lowering in homozygous disease, where receptor-directed drugs underperform.

Show evidence (2 references)

PMID:23122768 SUPPORT Human Clinical

"Patients with homozygous familial hypercholesterolaemia respond inadequately to existing drugs."

States the therapeutic gap that LDLR-independent agents were developed to fill.

PMID:23122768 SUPPORT Human Clinical

"Four patients had aminotransaminase levels of more than five times the upper limit of normal, which resolved after dose reduction or temporary interruption of lomitapide."

Documents the hepatic toxicity signal that constrains dosing.

Lipoprotein Apheresis

Action: Therapeutic Procedure NCIT:C49236

Platform: Device

Extracorporeal physical removal of apoB-containing lipoproteins from plasma. Wholly independent of LDL receptor function and therefore effective in receptor-negative disease, but the effect rebounds between sessions and the vascular-access, time, and cost burden is substantial. Current consensus places it alongside pharmacotherapy as foundational in severe biallelic disease.

Mechanism Target:

INHIBITS Lifelong Elevation of Plasma LDL Cholesterol — Removes circulating LDL directly, requiring no receptor and no hepatic metabolic step.

Show evidence (1 reference)

PMID:37130090 SUPPORT Human Clinical

"Combination LDL-C-lowering therapy-both pharmacologic intervention and lipoprotein apheresis (LA)-is foundational."

Establishes apheresis as a foundational component of severe-disease management.

Show evidence (1 reference)

PMID:37130090 SUPPORT Human Clinical

"Addition of novel, efficacious therapies (i.e. inhibitors of proprotein convertase subtilisin/kexin type 9, followed by evinacumab and/or lomitapide) offers potential to attain LDL-C goal or reduce the need for LA."

Positions apheresis relative to the newer pharmacologic options.

Ezetimibe

Action: Pharmacotherapy NCIT:C15986

Agent: ezetimibe CHEBI:49040

Platform: Small molecule

Cholesterol-absorption inhibitor (NPC1L1) added to statin therapy when the LDL-C target is not reached - step two of the standard FH escalation. Curated here because its mechanism is receptor-dependent in the same sense statins are: blocking jejunal cholesterol uptake depletes hepatocyte cholesterol and drives a compensatory increase in LDL receptor, so like a statin it amplifies whatever receptor capacity the genotype leaves rather than bypassing the receptor. Statin-plus-ezetimibe reaches roughly 65-70% LDL-C reduction against 50-60% for a high-intensity statin alone.

Mechanism Target:

ACTIVATES Residual Receptor Activity Gates Receptor-Dependent LDL Lowering — Ezetimibe belongs on the receptor-dependent side of the gating relation, not the LDLR-independent side: it lowers LDL-C by inducing residual receptor, so its effect is bounded by the receptor capacity the genotype permits.

Show evidence (1 reference)

PMID:39076699 SUPPORT Other

"ezetimibe by blocking cholesterol uptake from the jejunum) result in a compensatory increase in LDL-R and subsequently enhanced LDL-C clearance."

States that ezetimibe lowers LDL-C through a compensatory increase in LDL receptor, which is what places it on the receptor-dependent side of the gating node alongside statins.

Show evidence (1 reference)

PMID:39076699 SUPPORT Other

"statins (alone or in combination with ezetimibe) demonstrated a significant reduction of future ASCVD events even in subjects with LDL-R defective forms"

Supports the event-level benefit of statin-plus-ezetimibe specifically in receptor-defective disease, the genotype stratum this entry curates.

Bempedoic Acid

Action: Pharmacotherapy NCIT:C15986

Agent: bempedoic acid CHEBI:149601

Platform: Small molecule

Oral ATP-citrate lyase inhibitor acting upstream of HMG-CoA reductase. Because it is a prodrug activated by a liver-specific enzyme absent from skeletal muscle, it is the guideline option for statin-intolerant patients - a common situation in a disease requiring lifelong high-intensity statin therapy. Like statins and ezetimibe it upregulates LDL receptor activity, so it sits on the receptor-dependent side of the gating relation. Reported LDL-C reduction was 22.3% in a pooled clinical-heterozygous-FH subgroup.

Mechanism Target:

ACTIVATES Residual Receptor Activity Gates Receptor-Dependent LDL Lowering — Inhibiting ATP-citrate lyase depletes hepatic cholesterol and upregulates LDL receptor activity by the same de-repression route statins use, so the effect is bounded by residual receptor capacity.

Show evidence (1 reference)

PMID:39076699 SUPPORT Other

"It acts as an inhibitor of adenosine triphosphate (ATP) citrate lyase, a hepatic enzyme that works upstream of HMG-CoA reductase with subsequent upregulation of LDL-R activity, similar to statins"

States the target and, critically for this entry, that the LDL-lowering effect runs through upregulation of LDL receptor activity.

Show evidence (1 reference)

PMID:36876740 SUPPORT Human Clinical

"Bempedoic acid, an ATP citrate lyase inhibitor, reduces low-density lipoprotein (LDL) cholesterol levels and is associated with a low incidence of muscle-related adverse events"

CLEAR Outcomes provides the outcome evidence justifying bempedoic acid as curated therapy rather than an investigational option.

Inclisiran (PCSK9-Directed siRNA)

Action: Pharmacotherapy NCIT:C15986

Agent: inclisiran CHEBI:176399

Platform: siRNA RNAi knockdown Delivery: Ligand conjugate Targeting: GalNAc

RNA target: PCSK9 hgnc:20001 PCSK9 mRNA

Dosing: once every 6 months every 182.5 days

Hepatocyte-targeted small interfering RNA that suppresses PCSK9 synthesis, given on days 1 and 90 and every six months thereafter. Mechanistically it reaches the same endpoint as a PCSK9 antibody - less PCSK9-mediated receptor degradation, therefore more receptor on the hepatocyte surface - by inhibiting hepatic PCSK9 production rather than neutralizing circulating protein, so it is equally receptor-dependent. ORION-9 (NCT03397121) tested it in adults with heterozygous FH.

Mechanism Target:

ACTIVATES Residual Receptor Activity Gates Receptor-Dependent LDL Lowering — Suppressing hepatic PCSK9 synthesis preserves receptor that would otherwise be degraded, so like the PCSK9 antibodies the effect requires a receptor that can be made and can function.

Show evidence (1 reference)

PMID:39076699 SUPPORT Other

"In contrast to anti-PCSK9 mAbs, inclisiran inactivates PCSK9 by inhibition of its hepatic synthesis"

Distinguishes the siRNA route to PCSK9 inactivation from antibody neutralization while placing both on the same receptor-preserving mechanism.

Show evidence (1 reference)

PMID:39076699 SUPPORT Other

"inclisiran represents a first-in-class cholesterol-lowering small interfering ribonucleic acid (siRNA), targeting PCSK9 messenger RNA (mRNA) in hepatocytes."

Establishes the modality and molecular target of the agent.

Liver Transplantation

Action: Organ Transplantation NCIT:C15289

Platform: Surgery

The limiting case of the receptor-dependent/receptor-independent axis: rather than amplifying or bypassing the patient's own receptor, orthotopic liver transplantation *supplies* a hepatic LDL receptor complement, which is why it can correct the biochemical defect in receptor-negative disease that no receptor-directed drug can reach. Reserved for homozygous patients whose LDL-C cannot be controlled by maximal medical therapy and apheresis, and constrained by operative risk and lifelong immunosuppression. Where severe cardiovascular involvement has already developed, combined heart-liver transplantation may be required, which is the argument for early listing rather than late rescue.

Mechanism Target:

ACTIVATES Reduced Functional Hepatic LDL Receptor Activity — Replacing the liver replaces the tissue that carries the defective receptor, restoring hepatic receptor capacity itself rather than modulating the residual capacity a mutant genotype leaves. This is the only curated intervention that acts on the receptor-activity node directly.

Show evidence (1 reference)

PMID:39815304 SUPPORT Human Clinical

"Accordingly, all 6 patients received orthotopic liver transplantations (OLT), with the result that significant postoperative reductions were observed in levels of TC and LDL."

Reports that supplying a donor liver lowers total and LDL cholesterol, which is the receptor-supply mechanism this edge asserts.

Show evidence (2 references)

PMID:39815304 SUPPORT Human Clinical

"In severe cases of HoFH, clinical signs and symptoms cannot be controlled well by non-surgical treatments, liver transplantation (LT) currently represents the viable option."

Places liver transplantation as the option of last resort when medical therapy fails, the clinical position curated here.

PMID:39815304 SUPPORT Human Clinical

"If severe cardiovascular involvement occurs, LT should be performed as soon as possible, otherwise combined heart-liver transplantation may be required."

Supports the timing argument in the description - that the cost of late listing is escalation to combined heart-liver transplantation.

Cardiovascular Risk Factor Modification

Action: Dietary Intervention NCIT:C15447

Platform: Behavioral / lifestyle

The receptor defect sets a high baseline arterial risk that conventional risk factors multiply. Smoking cessation, control of blood pressure and glycemia, weight management, physical activity, and reduced saturated and trans fat intake do not correct the LDL level but reduce absolute event risk.

Show evidence (1 reference)

PMID:24404629 SUPPORT Other

"Agents/circumstances to avoid: Smoking, high intake of saturated and trans unsaturated fat, sedentary lifestyle, obesity, hypertension, and diabetes mellitus."

The GeneReviews agents-and-circumstances-to-avoid list, which is what this treatment entry operationalizes.

🌍

Environmental Factors

2

High Saturated and Trans Fat Intake

GeneReviews covers FH across LDLR, APOB and PCSK9, so its statement is class-level rather than an LDLR-genotype-specific finding, and the UK Biobank lifestyle analysis pools carriers across the same three genes.

Dietary saturated and trans fat add to circulating LDL on top of the receptor-mediated clearance defect, so this exposure acts on the lipid node rather than only on the vascular outcome. The effect is small in absolute terms - trial evidence puts reduced saturated fat intake at a small reduction in LDL cholesterol - which is exactly why diet is additive to, and never a substitute for, lipid-lowering pharmacotherapy here: the inherited component of the LDL burden is present from birth, is not diet-derived, and is far larger than diet can move.

Show evidence (3 references)

PMID:24404629 SUPPORT Other

"Prevention of primary manifestations: Heart-healthy diet (including reduced intake of saturated fat and increased intake of soluble fiber to 10-20 g/day); increased physical activity; no smoking."

The corresponding dietary recommendation, which establishes reduced saturated fat intake as a modifiable exposure in FH management.

PMID:35294538 SUPPORT Human Clinical

"Among carriers, a favorable lifestyle conferred 86% lower risk of CAD compared with an unfavorable lifestyle (hazard ratio, 0.14 [95% CI, 0.04-0.41])."

Quantifies how much the modifiable exposures move the arterial outcome in people who already carry an FH variant. The 4-point lifestyle score bundles diet, exercise, smoking and obesity, so it does not isolate this single exposure, and carriers are pooled across LDLR, APOB and PCSK9 rather than reported for LDLR alone.

PMID:35294538 SUPPORT INDIRECT Human Clinical

"Healthy lifestyle score was only minimally associated with LDL cholesterol concentrations."

Recorded because it qualifies the item above rather than reinforcing it. In this cohort the lifestyle score cut coronary risk by 86% while barely moving LDL cholesterol, so most of that benefit did not run through the plasma LDL node this exposure is wired to. It is cited here as a limit on how much of the diet effect the lipid node carries, not as support for the edge, which rests on the Cochrane trials above.

Mechanism Target:

EXACERBATES Lifelong Elevation of Plasma LDL Cholesterol — Dietary fat intake adds to the circulating LDL burden already produced by the inherited receptor deficit, acting on the same plasma LDL quantity.

Show evidence (3 references)

PMID:32827219 SUPPORT Human Clinical

"small reductions in weight, serum total cholesterol, LDL cholesterol and BMI"

Cochrane review of randomised trials of reduced saturated fat intake, which is the source that actually measures this exposure against the node it is attached to. Note the magnitude it reports: small. The trials are in general populations, not FH cohorts.

PMID:32827219 SUPPORT Human Clinical

"greater reductions in saturated fat (reflected in greater reductions in serum cholesterol) resulted in greater reductions in risk of CVD events, explaining most heterogeneity between trials."

The dose-response that carries the exposure through this node to the arterial outcome, and the reason the edge is drawn to the lipid node rather than straight to the vascular one.

PMID:24404629 SUPPORT Other

"Agents/circumstances to avoid: Smoking, high intake of saturated and trans unsaturated fat, sedentary lifestyle, obesity, hypertension, and diabetes mellitus."

GeneReviews names high saturated and trans fat intake among the exposures to avoid in FH; it is grouped here with the exposures acting at the lipid level rather than on the arterial wall.

Tobacco Smoking

GeneReviews covers FH across LDLR, APOB and PCSK9, so its statement is class-level rather than an LDLR-genotype-specific finding, and the UK Biobank lifestyle analysis pools carriers across the same three genes.

Smoking's contribution in FH runs predominantly through the arterial wall rather than through plasma LDL, which is why it is attached to the endothelial node and not to a lipid one. Set against an LDL burden that begins at birth and accumulates for decades before the first event, cessation matters in absolute terms: carriers move between roughly 35% and 66% estimated coronary risk by age 75 across lifestyle categories. That is an absolute-risk argument, not a claim that carriers benefit more per unit of exposure than anyone else - the study reporting those figures found no significant interaction between carrier status and lifestyle.

Show evidence (3 references)

PMID:24404629 SUPPORT Other

"reduce CAD risk factors including cessation of smoking, regular physical activity, healthy diet, and weight control"

Smoking cessation is named as part of the coronary risk-factor reduction that runs alongside lipid lowering in FH management.

PMID:35294538 SUPPORT Human Clinical

"Among carriers, a favorable lifestyle conferred 86% lower risk of CAD compared with an unfavorable lifestyle (hazard ratio, 0.14 [95% CI, 0.04-0.41])."

The size of the lifestyle effect on coronary risk among FH-variant carriers. The 4-point score bundles diet, exercise, smoking and obesity, so it does not isolate smoking, and carriers are pooled across LDLR, APOB and PCSK9.

PMID:35294538 SUPPORT Human Clinical

"Similar to the general population, individuals who carry familial hypercholesterolemia variants are likely to benefit from lifestyle interventions to reduce their risk of CAD."

Recorded to bound the previous item. The same analysis found no significant interaction between carrier status and lifestyle, so the benefit of cessation in carriers is a matter of their higher absolute risk rather than of a steeper response to the exposure.

Mechanism Target:

EXACERBATES Endothelial Dysfunction and Subendothelial LDL Retention — Smoking aggravates endothelial dysfunction, the permissive condition for subendothelial retention of the apoB-containing particles that the receptor defect leaves in circulation.

Show evidence (1 reference)

PMID:24404629 SUPPORT Other

"Agents/circumstances to avoid: Smoking, high intake of saturated and trans unsaturated fat, sedentary lifestyle, obesity, hypertension, and diabetes mellitus."

GeneReviews lists smoking first among exposures to avoid in FH. The node it is attached to reflects that smoking acts on the arterial wall rather than on plasma LDL.

🔬

Biochemical Markers

3

Plasma LDL Cholesterol (Increased)

Show evidence (1 reference)

PMID:24404629 SUPPORT Human Clinical

"A clinical diagnosis of FH can be established in a proband with characteristic clinical features and significantly elevated LDL-C levels (typically >190 mg/dL in adults and >160 mg/dL in children)."

Establishes LDL-C as the diagnostic analyte and gives its thresholds.

Plasma Apolipoprotein B (Increased)

Show evidence (1 reference)

PMID:28475941 SUPPORT Human Clinical

"Patients with null variants have a more severe phenotype than patients with defective variants, presenting with significantly higher levels of atherogenic particles (total cholesterol, LDL-cholesterol and apolipoprotein B)."

Names apolipoprotein B among the atherogenic particle measures elevated in this disease, and shows it separating null from defective allele classes.

Lipoprotein(a) (Variable)

Show evidence (2 references)

PMID:24632281 SUPPORT Human Clinical

"On multivariate analysis, Lp(a) was an independent predictor of cardiovascular disease."

Establishes Lp(a) as an independent cardiovascular risk predictor within FH.

PMID:24632281 SUPPORT Human Clinical

"The risk of CVD is higher in those patients with an Lp(a) level >50 mg/dl and carrying a receptor-negative mutation in the LDLR gene compared with other less severe mutations."

Shows Lp(a) risk interacting with the receptor class - the highest risk stratum is receptor-negative genotype plus high Lp(a).

🔬

Diagnosis

2

Molecular Genetic Testing of LDLR

Sequencing of LDLR together with APOB and PCSK9, plus deletion/duplication analysis, since exon-level copy-number changes are a real and sequencing-invisible part of the LDLR allelic series. Variant interpretation should follow the ClinGen FH Variant Curation Expert Panel's LDLR-specific specification of the ACMG/AMP framework rather than the generic rules, which is what makes a confident pathogenic call - and therefore cascade testing of relatives - possible.

Show evidence (2 references)

PMID:24404629 SUPPORT Human Clinical

"The molecular diagnosis of FH can be established by identification of heterozygous or biallelic pathogenic variants in APOB (variants that impair binding of LDL-C to the LDL receptor), LDLR, or PCSK9 (gain of function); or rarely, identification of biallelic pathogenic variants in LDLRAP1."

States the molecular diagnostic route and the genes tested.

PMID:34906454 SUPPORT Human Clinical

"Establishment of these guidelines as the new standard in the clinical laboratory setting will result in a more evidence-based, harmonized method for LDLR variant classification worldwide, thereby improving the care of patients with FH."

Names the gene-specific interpretation standard that governs the diagnostic call.

Functional Characterization of LDLR Variants

Cell-based assays - LDL binding and uptake by flow cytometry with fluorescent LDL, receptor expression by immunofluorescence or Western blot, and receptor localization by confocal microscopy - performed in receptor-deficient CHO-ldlA7 cells transfected with the patient allele. These assays do two things no in silico predictor can: they resolve variants of uncertain significance into a pathogenicity call, and they assign the allele to a functional class, which is the input to genotype-guided therapy selection.

Show evidence (3 references)

PMID:25386756 SUPPORT In Vitro

"Additionally confocal microscopy allowed the assignment of different class mutation to the variants assayed."

Establishes class assignment as an output of the functional assay.

PMID:31106925 SUPPORT In Vitro

"This approach allows us to confirm the genetic diagnosis of FH, avoiding the classification as "uncertain significant variants", and therefore, carry out cascade family screening."

States the clinical consequence of functional characterization - VUS resolution enabling cascade screening.

PMID:37847331 SUPPORT Computational

"Despite their contributions, a definitive diagnosis of a genetic variant necessitates functional validation through in vitro characterization or cascade screening."

States that computational prediction alone is insufficient, which is why the functional assay is curated as its own diagnostic modality.

📈

Progression

3

Presymptomatic biochemical disease (birth onward)

LDL cholesterol is elevated from birth because the receptor defect is constitutional. Heterozygotes are typically asymptomatic through childhood while arterial cholesterol exposure accumulates; this is the window in which treatment has the largest effect on lifetime risk.

Show evidence (1 reference)

PMID:24404629 SUPPORT Human Clinical

"Monitor lipid levels from age two years"

Surveillance from age two reflects a biochemical phenotype that is present long before any clinical event.

Extravascular cholesterol deposition (childhood to adulthood)

Tendon xanthoma, xanthelasma, and premature corneal arcus accumulate with age and with the height of the LDL burden. They are specific but insensitive - their absence does not exclude the diagnosis.

Show evidence (1 reference)

PMID:24404629 SUPPORT Human Clinical

"Xanthomas (cholesterol deposits in tendons) may be visible in the Achilles tendons or tendons of the hands and worsen with age as a result of extremely high cholesterol levels."

Describes the age-dependent accumulation of tendon xanthoma.

Premature atherosclerotic cardiovascular disease

Coronary and proximal aortic plaque develops decades earlier than in the general population. In biallelic disease coronary events and calcific aortic valve disease can occur in childhood or adolescence.

Show evidence (1 reference)

PMID:24404629 SUPPORT Human Clinical

"Familial hypercholesterolemia (FH) is characterized by significantly elevated low-density lipoprotein cholesterol (LDL-C) that leads to atherosclerotic plaque deposition in the coronary arteries and proximal aorta at an early age and increases the risk of premature cardiovascular events such as..."

Describes early coronary/proximal aortic atherosclerosis in familial hypercholesterolemia, severe biallelic presentation and LDLR among its causes. The excerpt does not quantify the decades-earlier comparison.

📊

Prevalence

1

Molecularly diagnosed familial hypercholesterolemia cohorts

Unknown Unknown

Recorded as a share of molecularly solved FH rather than as a population rate. LDLR is by a wide margin the most common FH gene, but the reported share varies with referral criteria, panel design, and whether deletion/duplication analysis was performed, so the figure is carried as a quoted range with its source rather than normalized to a single number. Population prevalence of the FH phenotype as a whole belongs to the umbrella entry (MONDO:0005439) and is not restated here.

Show evidence (1 reference)

PMID:30306860 SUPPORT Human Clinical

"The most common (60-80%) FH cause is mutations of the LDL Receptor (LDLR) protein (6 classes with a different number of receptors and functionality)."

Quantifies the LDLR share of FH and names the receptor-class scheme this entry models.

🔀

Differential Diagnoses

6

Conditions with similar clinical presentations that must be differentiated from LDLR-Related Familial Hypercholesterolemia:

Familial defective apolipoprotein B-100 (APOB)

Overlapping Features The ligand-side mirror of this entry. Clinically indistinguishable at the bedside and separated only by molecular testing: here the receptor is defective, there the receptor is normal and the apoB-100 ligand it must recognize is not. Curated separately as Familial_Defective_Apolipoprotein_B-100 (MONDO:0007751). LDL-C elevation is generally milder than in LDLR-related disease.

Show evidence (1 reference)

PMID:24404629 SUPPORT Human Clinical

"The molecular diagnosis of FH can be established by identification of heterozygous or biallelic pathogenic variants in APOB (variants that impair binding of LDL-C to the LDL receptor), LDLR, or PCSK9 (gain of function); or rarely, identification of biallelic pathogenic variants in LDLRAP1."

GeneReviews names APOB as an alternative molecular cause of the same clinical picture and specifies its distinguishing mechanism - impaired binding of LDL-C to the receptor rather than a defective receptor.

Autosomal dominant hypercholesterolemia 3 (PCSK9 gain of function)

Overlapping Features The regulator-side member of the dominant trio. The receptor gene is intact; a gain-of-function PCSK9 variant degrades normal receptor prematurely, so receptor number falls without any receptor defect. Curated separately as Autosomal_Dominant_Hypercholesterolemia_3 (MONDO:0011369). The practical consequence is therapeutic: PCSK9-directed agents address the causal lesion there, whereas here they amplify a residual receptor.

Show evidence (1 reference)

PMID:24404629 SUPPORT Human Clinical

"The molecular diagnosis of FH can be established by identification of heterozygous or biallelic pathogenic variants in APOB (variants that impair binding of LDL-C to the LDL receptor), LDLR, or PCSK9 (gain of function); or rarely, identification of biallelic pathogenic variants in LDLRAP1."

GeneReviews lists PCSK9 gain of function as a distinct molecular route to the same phenotype.

Autosomal recessive hypercholesterolemia (LDLRAP1)

Overlapping Features The phenocopy of this entry acting in trans. LDLRAP1 encodes the adaptor that couples the receptor to the clathrin endocytic machinery, so biallelic loss produces functionally the same internalization failure as a class 4 LDLR allele while the receptor itself is normal. Recessive rather than dominant, so parents are typically unaffected - the pedigree pattern is usually what separates it clinically.

Show evidence (1 reference)

PMID:24404629 SUPPORT Human Clinical

"or rarely, identification of biallelic pathogenic variants in LDLRAP1."

GeneReviews records LDLRAP1 as the rare biallelic route to a clinical FH diagnosis, distinguishing it from the dominant genes by inheritance.

Polygenic hypercholesterolemia

Overlapping Features The most common alternative explanation for a clinical FH phenotype with no identified monogenic variant: the cumulative effect of many small LDL-C raising alleles can reach the same LDL-C range as a monogenic defect. Distinguishing it matters because cardiovascular risk, cascade-testing yield, and treatment responsiveness differ from monogenic disease, and because a negative LDLR test does not exclude clinical FH.

Show evidence (1 reference)

PMID:39076699 SUPPORT Other

"would suggest polygenic causes of FH, where small but cumulative effects of several LDL-C raising alleles can cause the LDL-C increase up to the same range as that"

States that polygenic burden can reproduce the monogenic LDL-C range, which is what makes it the principal differential for a variant-negative clinical FH phenotype.

Elevated lipoprotein(a) mimicking familial hypercholesterolemia

Overlapping Features Not a separate disease so much as a measurement artefact that produces the same referral. Conventional LDL-C assays cannot separate LDL-cholesterol from lipoprotein(a)-cholesterol because the particles overlap in density, so a high Lp(a) inflates measured LDL-C and can push a patient into a clinical FH category they do not belong in. Relevant to this entry because Lp(a) is also genuinely elevated in FH and is curated as a biomarker here.

Show evidence (1 reference)

PMID:39076699 SUPPORT Other

"Conventional assays for LDL-C determination quantify a composite of atherogenic cholesterol, which is attributable not only to LDL-C, but also to lipoprotein(a)-cholesterol (Lp(a)-C) due to their overlapping densities."

Explains the assay overlap that lets high Lp(a) masquerade as the elevated LDL-C used to make a clinical FH diagnosis.

Sitosterolemia, dysbetalipoproteinemia, and cholesteryl ester storage disease

Overlapping Features Distinctive non-FH inherited dyslipidemias that can present with severe hypercholesterolemia and xanthoma and so enter the differential of a young patient with very high LDL-C and no LDLR variant - sitosterolemia (ABCG5 / ABCG8), dysbetalipoproteinemia (APOE), and cholesteryl ester storage disease / lysosomal acid lipase deficiency (LIPA). Each has its own mechanism and, importantly, its own treatment, so misassignment to FH has therapeutic consequences.

Show evidence (1 reference)

PMID:39076699 SUPPORT Other

"some of these genes might also cause distinctive non-FH syndromes such as sitosterolemia (ABCG5), dysbetalipoproteinemia (APOE) or cholesteryl ester storage disease (LIPA)"

Names the non-FH inherited dyslipidemias that share the severe hypercholesterolemia presentation.

📊

Related Datasets

3

LDLR variant classification through activity-normalized prime editing screening geo:GSE329001

Pooled activity-normalized prime-editing screen installing 5,184 LDLR coding variants in a human cell line and reading out LDL-cholesterol uptake, with each pegRNA paired to a genotypic outcome reporter so phenotypic scores can be corrected for editing efficiency. Manually relevance-triaged: the series is about the LDLR allelic series itself - which coding change breaks which step of receptor function - which is the axis this entry is built on, not merely about a gene that FH shares with other entries.

human MULTI OMICS PERTURBATION

PMID:42677454

Surfaced by `just discover-datasets` as a DIRECT candidate and confirmed against the linked publication before inclusion. The evidence item quotes the cached GEO record itself; the screen's scientific findings are cited from the publication on the corresponding experimental model instead.

Show evidence (1 reference)

GEO:GSE329001 SUPPORT In Vitro

"We developed an innovative, activity-normalized prime editing screening pipeline to measure the impact of 5,184 LDLR coding variants on LDL-cholesterol (LDL-C) uptake."

The repository record's own statement of what the series contains, which is what makes it the dataset for the allelic-series axis of this entry.

Transcriptomes of human monocytes from patients with familial hypercholesterolemia before and after statin treatment geo:GSE126352

RNA sequencing of circulating monocytes from familial hypercholesterolemia patients before and after three months of statin therapy, generated to ask whether lowering LDL reverses the trained-immunity phenotype of those cells. Relevant here to the monocyte arm of the arterial cascade and to what statin therapy does and does not undo. Relevance caveat: the cohort is defined clinically as familial hypercholesterolemia and the series does not report LDLR genotypes, so it is class-level rather than LDLR-specific.

human BULK RNA SEQ

PMID:31204280

Surfaced by `just discover-datasets` as a DIRECT candidate and confirmed against the linked publication before inclusion.

Show evidence (1 reference)

GEO:GSE126352 SUPPORT Human Clinical

"in this study we compared the transcriptomes of patients with hypercholesterolemia before and after statin treatment for 3 months"

The repository record's own statement of the design, which is what establishes the before/after statin comparison this record is cited for.

Circulating miRNA profile and coronary calcification in asymptomatic patients with familial hypercholesterolemia. geo:GSE178126

Microarray profiling of plasma microRNAs in asymptomatic familial hypercholesterolemia patients stratified by coronary artery calcium score on computed tomographic angiography. Relevant to the subclinical phase of the arterial arm - patients who already carry the lifelong LDL burden but have not yet had an event. Relevance caveat: the cohort is defined clinically and the series does not report LDLR genotypes, so it is class-level rather than LDLR-specific.

human MICROARRAY

PMID:38513437

Surfaced by `just discover-datasets` as a DIRECT candidate and confirmed against the linked publication before inclusion.

Show evidence (1 reference)

GEO:GSE178126 SUPPORT Human Clinical

"We used miRNA arrays to profile miRNAs isolated from plasma from familial hypercholesterolemia patients with (FH-W_CCS) or without (FH-WO_CCS) coronary calcium score by computed tomographic angiography"

The repository record's own statement of the stratification, which is what makes this series about the subclinical arterial phase rather than about FH generally.

🔬

Clinical Trials

4

NCT03399786 PHASE_III COMPLETED

ELIPSE HoFH. Randomized, double-blind, placebo-controlled trial of intravenous evinacumab in 65 patients with homozygous familial hypercholesterolemia, reporting results separately for null-null and non-null LDL-receptor genotypes - the trial that established LDLR-independent LDL lowering in receptor-negative disease.

Target Phenotypes: Increased LDL cholesterol concentration HP:0003141

Show evidence (1 reference)

clinicaltrials:NCT03399786 SUPPORT Human Clinical

"The primary objective of the study is to demonstrate the reduction of low-density lipoprotein cholesterol (LDL-C) by evinacumab intravenously (IV) in comparison to placebo after 24 weeks in patients with homozygous familial hypercholesterolemia (HoFH)."

States the trial's primary objective in the population relevant to this entry.

NCT04233918 PHASE_III COMPLETED

Three-part, single-arm, open-label study of evinacumab in paediatric patients with homozygous familial hypercholesterolemia, extending the LDLR-independent option to children, in whom receptor-negative disease presents earliest.

Target Phenotypes: Increased LDL cholesterol concentration HP:0003141

Show evidence (1 reference)

clinicaltrials:NCT04233918 SUPPORT Human Clinical

"The primary objective for Part B of the study is to demonstrate a reduction of low-density lipoprotein cholesterol (LDL-C) by evinacumab in pediatric (5 to 11 years of age) patients with HoFH."

States the trial's efficacy objective in the paediatric homozygous population.

NCT03397121 PHASE_III COMPLETED

ORION-9. Placebo-controlled, double-blind, randomized trial of inclisiran, a hepatocyte-targeted siRNA that suppresses PCSK9 synthesis, in adults with heterozygous familial hypercholesterolemia - a receptor-amplifying mechanism tested in the population that retains residual receptor.

Target Phenotypes: Increased LDL cholesterol concentration HP:0003141

Show evidence (1 reference)

clinicaltrials:NCT03397121 SUPPORT Human Clinical

"This is a Phase III, placebo-controlled, double-blind, randomized study in participants with HeFH and elevated LDL-C to evaluate the efficacy, safety, and tolerability of subcutaneous (SC) injection(s) of inclisiran."

States the trial design, population, and agent.

NCT06597006 PHASE_III RECRUITING

Two-part randomized study of inclisiran in children aged 2 to under 12 with homozygous familial hypercholesterolemia. Curated because it is the most directly on-thesis trial available for this entry: its enrolment criteria operationalize the gating relation itself, requiring documented biallelic null LDLR mutations and excluding children with poor prior response to a PCSK9 antibody - i.e. it tests a receptor-preserving agent in exactly the genotype stratum where receptor-directed therapy is predicted to fail.

Target Phenotypes: Increased LDL cholesterol concentration HP:0003141

Show evidence (1 reference)

clinicaltrials:NCT06597006 SUPPORT Human Clinical

"This is a pivotal phase III study designed to evaluate safety, tolerability, and efficacy of inclisiran in children (aged 2 to \<12 years) with homozygous familial hypercholesterolemia (HoFH) and elevated low density lipoprotein cholesterol (LDLC)."

States the design and the homozygous paediatric population; the genotype-specific enrolment detail is recorded in the description from the registry record rather than quoted, as the cached summary does not carry the eligibility text.

🧫

Experimental Models

4

J.D. fibroblast strain (internalization-defective LDLR alleles) PRIMARY_CELL_CULTURE

Cultured skin fibroblasts from subject J.D., one of 22 fibroblast strains from patients with the clinical phenotype of homozygous FH screened by Brown and Goldstein. This is the system in which the receptor mutation classes were defined: the other 21 strains bound labelled LDL either not at all (receptor-negative) or poorly (receptor-defective), while J.D. bound LDL normally and failed to internalize it, which is the observation that established internalization as a separable step and gave the entry its Class 4 allele. J.D. is a compound heterozygote, not a true homozygote: a maternal exon 13-15 deletion producing no functional protein, and a paternal Y807C allele producing a receptor that reaches the surface and binds LDL. The 1976 designation is a pre-molecular clinical label. The cellular phenotype is nonetheless cleanly internalization-defective, because the only receptor these cells display is the Y807C one.

Organism

human NCBITaxon:9606

Cell source

Patient-derived skin fibroblasts (homozygous FH probands)

Culture

Two-dimensional monolayer fibroblast culture

Publication

PMID:189940

Pathograph links

Defective Clustering in Clathrin-Coated Pits recapitulates fidelity: high observes: cellular The founding measurement of this node. Binding and internalization are assayed separately in the same cells, so the defect is localized to the internalization step rather than inferred from a lowered uptake total.

Limitations: Fibroblasts are not hepatocytes, and hepatic receptor activity is what sets plasma LDL; the strain establishes that the step exists and can be broken in isolation, not the quantitative hepatic consequence. The 1976 report also predates identification of the underlying LDLR sequence changes, so what it measures is the cellular phenotype and not the alleles, and the compound-heterozygous genotype means the strain reports the Y807C allele in the absence of a second functional receptor rather than a Class 4 allele in isolation.

Readouts

Internalization of receptor-bound 125I-LDL

Direction: DECREASED

Interpretation: Normal high-affinity binding alongside a profound internalization defect in the same cells is the direct measurement this node asserts. The 1976 assay recorded no detectable internalization; DECREASED rather than ABOLISHED is used because the expression-cloning work this entry also cites (PMID:3955657) later showed the Y807C receptor enters the cell slowly rather than not at all.

Show evidence (1 reference)

PMID:189940 SUPPORT In Vitro

"the cell surface receptor for plasma low density lipoprotein (LDL) was able to bind 125I-labeled LDL normally, but internalization of the receptor-bound lipoprotein failed to occur"

Reports the paired binding and internalization measurements grounding this readout.

Show evidence (1 reference)

PMID:189940 SUPPORT In Vitro

"the defect in this strain differed from the defects found in the fibroblasts from the other 21 FH homozygote strains in which the binding of 125I-LDL to the receptor was either absent (receptor-negative) or markedly reduced (receptor-defective)"

Establishes the contrast against the receptor-negative and receptor-defective strains, which is what makes this strain informative for internalization specifically rather than for receptor loss in general.

JD iPSC-derived hepatocyte-like cells IPSC_DERIVED_MODEL

Induced pluripotent stem cells reprogrammed from the same FH patient (JD) whose fibroblasts defined the internalization-defective class, differentiated into hepatocyte-like cells. Moving the identical genotype from fibroblast to hepatocyte is what makes this model informative for the plasma-clearance arm: it reads out the receptor defect in the cell type that actually clears circulating LDL, and it reproduces the drug-response behaviour as well as the uptake defect.

Organism

human NCBITaxon:9606

Cell source

Patient-derived (JD fibroblasts reprogrammed to iPSC)

Culture

Two-dimensional hepatocyte-like cell differentiation

Publication

PMID:22653811

Pathograph links

Impaired Receptor-Mediated Clearance of Plasma LDL recapitulates fidelity: moderate observes: cellular Patient-genotype hepatocyte-like cells are deficient in LDL-C uptake relative to controls, the cellular counterpart of the plasma clearance defect this node asserts.

Limitations: The node is an organism-level clearance claim and the measurement is cellular uptake in culture, so the step from one to the other is inferential. iPSC-derived hepatocyte-like cells are also immature relative to adult hepatocytes, and the comparison is between individuals rather than between isogenic corrected and uncorrected lines, so donor background is not controlled.

Readouts

LDL-cholesterol uptake by hepatocyte-like cells

Direction: DECREASED

Interpretation: Direct cellular measurement of the receptor-mediated uptake step that plasma clearance depends on.

Show evidence (1 reference)

PMID:22653811 SUPPORT In Vitro

"in contrast to control cells, FH iPSC-derived hepatocytes are deficient in LDL-C uptake"

Reports the uptake deficit grounding this readout.

Show evidence (1 reference)

PMID:22653811 SUPPORT In Vitro

"we produced iPSCs from JD a patient with mutations in the low-density lipoprotein receptor (LDLR) gene that result in familial hypercholesterolemia (FH)"

Establishes that the line carries a patient LDLR genotype, which is what makes its uptake behaviour informative for this node.

Residual Receptor Activity Gates Receptor-Dependent LDL Lowering recapitulates fidelity: moderate observes: cellular Control hepatocyte-like cells raise LDL uptake when given lovastatin and the FH cells do not. The block is not in the drug's proximal action: the same study reports that FH cells induce LDLR mRNA on lovastatin to a similar extent as controls. What the genotype bounds is the usefulness of that induction, because the additional receptor it produces is the defective receptor. That is the gating relation observed at the level of the hepatocyte itself.

Limitations: One patient genotype and one drug, measured as cellular uptake rather than plasma LDL-C, so the model shows the direction of the gating relation and not its dose-response across the allelic series. The node also covers receptor-independent agents, on which this model is silent.

Readouts

LDL uptake response to lovastatin

Direction: UNCHANGED

Interpretation: Absence of the drug-induced increase that control cells show is the cellular counterpart of a blunted receptor-dependent LDL-lowering response.

Show evidence (2 references)

PMID:22653811 SUPPORT In Vitro

"control but not FH iPSC-derived hepatocytes increase LDL uptake in response to lovastatin"

Reports the differential statin response grounding this readout.

+ 1 more reference

Show evidence (1 reference)

PMID:22653811 SUPPORT In Vitro

"these findings demonstrate that FH iPSC-derived hepatocytes recapitulate the complex pathophysiology of FH in culture"

The authors' own summary claim that the model reproduces FH hepatocyte behaviour, which is the basis for treating it as informative here.

Findings

The same model reports a second, non-clearance abnormality: FH hepatocyte-like cells oversecrete lipidated apolipoprotein B-100 roughly eight-fold over controls. This entry models the receptor defect as impaired clearance only, and that is a deliberate scope limit rather than a claim that clearance is the whole mechanism - the authors argue explicitly that hepatic apoB-lipoprotein overproduction contributes too. No pathophysiology node is asserted for it here because the human evidence for an LDLR-specific overproduction arm was not assessed in this curation round.

"FH iPSC-derived hepatocytes display a marked elevation in secretion of lipidated apolipoprotein B-100"

Show evidence (1 reference)

PMID:22653811 SUPPORT In Vitro

"FH iPSC-derived hepatocytes display a marked elevation in secretion of lipidated apolipoprotein B-100"

Reports the oversecretion result. Recorded as a finding rather than as a mechanism node so that the gap between this model's output and the entry's clearance-only pathograph is visible rather than silent.

CHO-ldlA7 heterologous LDLR variant expression assay CELL_LINE

Site-directed LDLR mutants expressed in CHO-ldlA7 cells, a Chinese hamster ovary line carrying no endogenous LDL receptor, with surface expression, LDL binding and LDL uptake read out separately by flow cytometry. This is the assay behind the entry's Functional Characterization of LDLR Variants diagnostic item, and because it resolves the three steps separately it is the assay family from which class assignment is made - the class call itself is a separate claim, cited on that diagnostic item (PMID:25386756) rather than here. This paper anchors the model because it states the system and the readouts most explicitly; the larger ClinGen-linked characterization effort (PMID:34906454) is cited elsewhere in the entry.

Organism

Chinese hamster NCBITaxon:10029

Cell source

LDLR-null cell line (CHO-ldlA7) transfected with the allele under test

Culture

Two-dimensional monolayer culture with transient LDLR expression

Publication

PMID:34167030

Pathograph links

Reduced Functional Hepatic LDL Receptor Activity measures fidelity: moderate observes: cellular Quantifies the residual activity a given LDLR allele supports, resolved into the three separable steps - surface expression, binding, uptake - that distinguish the receptor classes from one another.

Limitations: A hamster ovary line transiently overexpressing a human receptor is not a hepatocyte: expression level, trafficking machinery and lipoprotein milieu all differ, so the assay ranks alleles against each other rather than predicting an individual's hepatic receptor activity. This study characterized 13 variants and used a 60% activity cut-off, which is an operational threshold rather than a measured physiological boundary; setting 13 against the more than 2300 variants catalogued elsewhere in this entry is a comparison drawn here, not one the paper makes.

Readouts

Surface expression, LDL binding and LDL uptake by flow cytometry

Direction: DECREASED

Interpretation: Residual activity below the assay threshold in one or more of the three steps is what marks an allele as functionally impairing.

Show evidence (1 reference)

PMID:34167030 SUPPORT In Vitro

"cell surface expression, binding and uptake of FITC-LDL were assessed by flow cytometry and Western blot"

Names the three measurements that constitute this readout.

Show evidence (2 references)

PMID:34167030 SUPPORT In Vitro

"Different LDLR mutants were generated by site-directed mutagenesis and expressed in CHO-ldlA7 cells lacking endogenous expression of LDLR."

Describes the null-background heterologous system, which is what lets the readout be attributed to the introduced allele.

+ 1 more reference

Activity-normalized prime editing saturation screen of LDLR coding variants CELL_LINE

Pooled prime-editing screen installing 5,184 LDLR coding variants at the endogenous locus in human cells and scoring each for LDL-cholesterol uptake, with a genotypic outcome reporter paired to every guide so scores can be normalized for editing efficiency. It is the saturation counterpart of the one-variant-at-a-time heterologous assay above: instead of ranking a handful of alleles it maps the whole coding series onto a continuous activity scale, and because the variant sits at the endogenous locus it also catches splice-altering coding changes that complementary-DNA constructs cannot express.

Organism

human NCBITaxon:9606

Cell source

Human cells carrying prime-edited LDLR at the endogenous locus

Culture

Pooled two-dimensional culture with fluorescence-based LDL uptake sorting

Publication

PMID:42677454

Pathograph links

Reduced Functional Hepatic LDL Receptor Activity measures fidelity: moderate observes: cellular Measures residual LDL uptake for each of 5,184 coding variants, turning the receptor-activity axis this node represents into a per-allele quantity that separates known pathogenic from known benign variants and tracks LDL-C in an independent human cohort.

Limitations: Uptake is a single composite readout, so unlike the stepwise flow cytometry assay it does not resolve which step of the receptor itinerary an allele breaks and therefore does not by itself assign a receptor class. It covers coding variants only, leaving promoter changes and exon-level deletions untouched, and the functional score is calibrated as evidence toward classification rather than as a diagnosis in its own right.

Readouts

Per-variant LDL-cholesterol uptake score

Direction: DECREASED

Interpretation: A continuous activity score per allele, anchored by the separation of pathogenic from benign ClinVar variants and by concordance with measured LDL-C in carriers.

Show evidence (1 reference)

PMID:42677454 SUPPORT In Vitro

"The resulting scores capture a continuous spectrum of functional effects, robustly separate pathogenic versus benign ClinVar variants, and show concordance with LDL-C levels in UK Biobank participants."

Reports both the score itself and the two external anchors that make it interpretable as receptor activity.

Show evidence (2 references)

PMID:42677454 SUPPORT In Vitro

"We developed the first activity-normalized prime editing screening pipeline to measure the impact of 5184 LDLR coding variants on LDL-cholesterol (LDL-C) uptake."

Describes the assay and its scale, which is what makes it informative for the receptor-activity node across the allelic series rather than for one allele.

+ 1 more reference

The screen also reports a cluster of gain-of-function variants in ligand-binding repeat 5, at least some of which raise LDL uptake through increased apolipoprotein B interaction. Those alleles are not part of this disease - they are the mirror image of it - and are noted here only because they come from the same experiment and bear on therapeutic genome editing.

🐁

Animal Models

3

Ldlr-knockout mouse

The founding genetic model. Viable and fertile, with a selective rise in IDL and LDL and a demonstrated prolongation of apoB-lipoprotein clearance, and reversible by hepatic re-expression of the human receptor - which closes the causal loop between receptor absence and hypercholesterolemia.

Species

Mouse

Genotype

Ldlr-/- (homologous recombination in embryonic stem cells)

Publication

PMID:8349823

Pathograph links

Impaired Receptor-Mediated Clearance of Plasma LDL recapitulates fidelity: high Directly measures the clearance defect that this node represents, in the cleanest possible genetic background - complete receptor absence.

Limitations: Murine lipoprotein metabolism is apoB48- and HDL-dominated rather than LDL-dominated, so absolute cholesterol levels are far below human homozygous FH and spontaneous atherosclerosis on chow is limited; the model reproduces the clearance defect faithfully but not the human lipoprotein distribution or the arterial disease burden.

Readouts

Plasma clearance half-life of radiolabelled VLDL and LDL

Direction: INCREASED

Interpretation: Prolonged half-life is the direct measurement of the clearance defect; normal HDL clearance in the same animals shows the defect is ligand-specific.

Show evidence (1 reference)

PMID:8349823 SUPPORT Model Organism

"The half-lives for intravenously administered 125I-VLDL and 125I-LDL were prolonged by 30-fold and 2.5-fold, respectively, but the clearance of 125I-HDL was normal in the LDLR-/- mice."

Reports the measured clearance half-lives underlying this readout.

Show evidence (1 reference)

PMID:8183926 SUPPORT Model Organism

"LDLR(-/-) mice had a relatively isolated elevation in plasma LDL"

Confirms that the model isolates the LDL clearance arm rather than producing a generalized dyslipidemia.

Reduced Functional Hepatic LDL Receptor Activity rescues fidelity: high Restoring hepatic LDL receptor expression by adenoviral delivery normalized the elevated IDL/LDL within four days, demonstrating that the receptor deficit is both necessary and sufficient for the phenotype in this model.

Limitations: Adenoviral rescue is acute and supraphysiological hepatic overexpression, not a model of the endogenous allelic series; it establishes sufficiency of receptor restoration, not the dose-response of partial residual activity.

Readouts

Plasma IDL/LDL cholesterol after hepatic LDLR re-expression

Direction: RESTORED

Interpretation: Normalization on receptor restoration is the rescue arm of the causal claim.

Show evidence (1 reference)

PMID:8349823 SUPPORT Model Organism

"The elevated IDL/LDL level of LDLR-/- mice was reduced to normal 4 d after the intravenous injection of a recombinant replication-defective adenovirus encoding the human LDL receptor driven by the cytomegalovirus promoter."

Reports the rescue measurement.

Show evidence (1 reference)

PMID:8349823 SUPPORT Model Organism

"The virus restored expression of LDL receptor protein in the liver and increased the clearance of 125I-VLDL."

Confirms that the rescue acted through restored hepatic receptor protein.

Watanabe heritable hyperlipidemic (WHHL) rabbit

A spontaneously arising LDL-receptor-deficient rabbit strain and its coronary-atherosclerosis-prone and myocardial-infarction-prone derivatives. Rabbit lipoprotein metabolism is far closer to human than murine, and this is the model in which the LDL receptor pathway hypothesis - derived from cultured fibroblasts - was shown to hold in a whole animal, and in which the arterial consequences of lifelong receptor deficiency were worked out.

Species

Rabbit

Genotype

Naturally occurring homozygous LDL receptor deficiency

Publication

PMID:31748469

Pathograph links

Endothelial Dysfunction and Subendothelial LDL Retention recapitulates fidelity: high Spontaneous, diet-independent hypercholesterolemia from receptor deficiency drives the initiating arterial events - oxidized LDL accumulation, endothelial adhesion molecule expression, and monocyte infiltration.

Limitations: Rabbits lack the human coronary anatomy and plaque-rupture triggers in full, and the reviewed strain history reports that lesion rupture in this model requires secondary mechanical forces such as spasm, so event generation is not a faithful analogue of human acute coronary syndrome.

Readouts

Arterial intimal macrophage infiltration and oxidized LDL accumulation

Direction: INCREASED

Interpretation: Histological demonstration of the initiating steps of atherogenesis in a receptor-deficient animal.

Show evidence (1 reference)

PMID:31748469 SUPPORT Model Organism

"Oxidized LDL accumulates in the arterial wall, monocyte adhesion molecules are expressed on arterial endothelial cells, and monocyte-derived macrophages infiltrate the arterial intima, resulting in the formation and progression of atherosclerosis."

Reports the arterial findings underlying this readout.

Show evidence (1 reference)

PMID:31748469 SUPPORT Model Organism

"The main part of human lipoprotein metabolism has been elucidated, and the low-density lipoprotein (LDL) receptor pathway hypothesis derived from studies using fibroblasts was proven in vivo."

Establishes this strain as the in vivo proof of the receptor pathway, which is why it is informative for the arterial arm.

LDLR-knockout cynomolgus monkey

A genome-edited non-human primate model. Plasma cholesterol reached levels comparable to human homozygous FH, periocular xanthoma appeared within the first year, and the animals were strongly resistant to lipid-lowering medication - the primate counterpart of the receptor-negative pharmacological phenotype.

Species

Cynomolgus monkey

Genotype

LDLR knockout by genome editing (six founder animals)

Publication

PMID:37730951

Pathograph links

Residual Receptor Activity Gates Receptor-Dependent LDL Lowering recapitulates fidelity: moderate Complete receptor knockout reproduces the drug-refractory phenotype that defines receptor-negative homozygous disease.

Limitations: Six founder animals, possible mosaicism from editing, short follow-up, and the report characterizes drug resistance in aggregate rather than drug-by-drug, so it supports the direction of the gating relation but not an agent-specific magnitude.

Readouts

LDL cholesterol response to lipid-lowering medication

Direction: UNCHANGED

Interpretation: Failure to respond in a total-knockout primate is the model-side counterpart of the absent response in receptor-negative patients.

Show evidence (1 reference)

PMID:37730951 SUPPORT Model Organism

"The LDLR KO monkeys were also strongly resistant to medications for hypercholesterolemia."

Reports the drug-resistance observation underlying this readout.

Show evidence (1 reference)

PMID:37730951 SUPPORT Model Organism

"The levels of plasma cholesterol and triglyceride were quite high in the monkeys, and were similar to those in FH patients with homozygous mutations in the LDLR gene."

Establishes that the model reaches human homozygous-FH lipid levels, which is what makes its drug-response behaviour informative.

{ }

Source YAML

click to show

name: LDLR-Related Familial Hypercholesterolemia
creation_date: "2026-08-19T00:00:00Z"
description: >
  LDLR-related familial hypercholesterolemia (familial hypercholesterolemia 1,
  FHCL1; hyperlipoproteinemia type 2A) is the receptor-side form of familial
  hypercholesterolemia and the form for which the disease was originally
  defined. The low-density lipoprotein receptor is a cell-surface transmembrane
  protein that binds apoB-100-containing LDL particles and delivers them to the
  lysosome for degradation, and hepatic LDLR accounts for most clearance of
  plasma LDL. Germline pathogenic variants in LDLR reduce the number of
  functional receptors on the hepatocyte surface, LDL residence time in plasma
  lengthens, and LDL cholesterol is elevated from birth, producing cumulative
  arterial cholesterol exposure, premature atherosclerotic cardiovascular
  disease, and extravascular cholesterol deposition as tendon xanthoma,
  xanthelasma, and corneal arcus.

  What distinguishes this entry from its siblings is the *allelic series*. LDLR
  is a modular mosaic protein whose receptor itinerary - synthesis, folding and
  ER-to-Golgi export, surface presentation, ligand binding, clathrin-mediated
  internalization, endosomal ligand release, and recycling - can be interrupted
  at any step, and the classical five (sometimes six) mutation classes name
  which step a given allele breaks. That is not decorative taxonomy: how much
  receptor activity survives sets the ceiling on every receptor-dependent
  therapy. Statins and PCSK9-directed agents both work by putting *more* LDL
  receptor on the hepatocyte surface, so their effect is bounded by the
  receptor capacity the genotype permits. That bound has been demonstrated
  directly only for PCSK9-directed therapy, where LDL-C fell in
  receptor-defective homozygotes and not at all in the two receptor-negative
  patients studied (PMID:24014831); whether statins are equally null-dependent
  is not established here, and the entry's own cited review reports statins
  helping both homozygous and heterozygous patients. The LDLR-independent
  agents lomitapide, evinacumab, and lipoprotein apheresis act upstream of or
  around the receptor and so are expected to be genotype-independent - shown
  with genotype stratification for evinacumab, and not stratified for the
  other two. This entry curates the receptor
  itinerary, the class-to-step mapping, and the residual-activity-gates-therapy
  relation as its own mechanism graph.
category: Mendelian
synonyms:
- Hypercholesterolemia, familial, 1
- FHCL1
- Familial hypercholesterolemia type 1
- LDL receptor disorder
- LDL receptor deficiency
- Hyperlipoproteinemia type 2A
- Familial hypercholesterolemic xanthomatosis
- Autosomal dominant hypercholesterolemia 1
disease_term:
  preferred_term: LDLR-Related Familial Hypercholesterolemia
  term:
    id: MONDO:0007750
    label: hypercholesterolemia, familial, 1
parents:
- Familial Hypercholesterolemia
notes: >
  Scope: curated as a standalone Disease rather than folded into
  kb/disorders/Familial_Hypercholesterolemia.yaml (MONDO:0005439). Four
  reasons. (1) MONDO models MONDO:0007750 as a distinct is_a child of
  MONDO:0005439, anchored on OMIM:143890 and the synonym "LDL receptor
  disorder". (2) The umbrella entry's has_subtypes axis is *zygosity*
  (heterozygous / homozygous), not gene, so a gene-defined entity has no place
  on it without mixing two orthogonal axes. (3) The two other dominant FH genes
  already have sibling entries curated on exactly this rationale -
  Familial_Defective_Apolipoprotein_B-100 (MONDO:0007751, APOB) and
  Autosomal_Dominant_Hypercholesterolemia_3 (MONDO:0011369, PCSK9) - and
  leaving the receptor-side form as the one unmodelled member of the trio makes
  the set incoherent. (4) The mechanism graph curated here is deliberately NOT
  the umbrella's: the umbrella models a single "LDL receptor deficiency" entry
  point into a shared LDL-to-atherosclerosis pathway, whereas this entry
  elaborates the LDL receptor's own itinerary into per-step nodes (synthesis,
  ER-to-Golgi export, surface binding, clathrin-mediated internalization,
  endosomal release and recycling), maps the classical mutation classes onto
  those steps, and carries the residual-receptor-activity node that gates
  response to receptor-dependent therapy. That last relation is what makes the
  allelic series clinically actionable and it is not modelled anywhere else in
  the knowledge base.

  Deliberately NOT duplicated from the umbrella entry: the EHR case-finding
  phenotype algorithms (SEARCH, FAMCAT, FIND FH), the general FH prevalence
  and cascade-screening apparatus, the environmental risk-factor block, and the
  APOB/PCSK9/LDLRAP1/APOE arms. Cite MONDO:0005439 for the disorder as a class;
  cite this entry for receptor-side mechanism.

  Named Entity Confusion preflight (dismech NEC SOP): the hypercholesterolemia
  series is a high-NEC-risk numbered-and-lettered class (FH1/LDLR vs familial
  defective apoB-100 "type B"/APOB vs ADH3/PCSK9). `just preflight-dr` returned
  SKIP because MONDO records no RO:0004003 causal gene for MONDO:0007750, so
  the manual checks were run: the report's OMIM (143890) matches the MONDO
  xref exactly; gene mentions in the report are dominated by LDLR (70) over
  PCSK9 (19) and APOB (3); and the MONDO synonym list ("LDL receptor
  disorder", "hyperlipoproteinemia, type 2A") points at the receptor-side
  entity and does not collide with the labels or synonyms of MONDO:0007751 or
  MONDO:0011369. Mechanistic claims here are anchored on LDLR publications;
  PCSK9 appears only where a PCSK9-directed *drug* acts on the LDL receptor,
  which is receptor-side biology, not the ADH3 disease.

  evidence_source convention for the GeneReviews chapter (PMID:24404629):
  statements taken from its Clinical Characteristics, Diagnosis and Genetic
  Counseling sections report human patient observations and are tagged
  HUMAN_CLINICAL, while statements taken from its Management and
  Agents/Circumstances-to-Avoid sections are expert recommendations rather than
  reported data and are tagged OTHER. The mix of two evidence_source values
  against a single PMID in this file is deliberate, not drift. Separately, the
  chapter covers FH as a class across LDLR, APOB and PCSK9, so items citing it
  are class-level rather than LDLR-specific; that limitation is recorded in
  each item's explanation, and in the notes of the environmental exposures
  drawn from it.
references:
- reference: PMID:24404629
  title: "Familial Hypercholesterolemia."
  tags:
  - GeneReviews
  findings:
  - statement: >-
      Clinical characteristics. GeneReviews describes the FH clinical spectrum
      that LDLR-related FH defines - premature atherosclerotic plaque in the
      coronary arteries and proximal aorta, angina and myocardial infarction,
      tendon xanthoma, xanthelasma, and early corneal arcus, with calcific
      aortic valve disease and childhood-onset coronary artery disease in
      biallelic disease. The chapter covers FH as a class across LDLR, APOB and
      PCSK9, so it is class-level rather than LDLR-specific evidence and is
      cited as such throughout this entry.
    supporting_text: >-
      increases the risk of premature cardiovascular events such as angina and
      myocardial infarction
  - statement: >-
      Diagnosis and testing. GeneReviews gives the untreated LDL-C thresholds
      for a clinical FH diagnosis and names LDLR as one of three molecular
      routes to FH - the receptor-side route that defines this entry.
    supporting_text: >-
      The molecular diagnosis of FH can be established by identification of
      heterozygous or biallelic pathogenic variants in APOB (variants that
      impair binding of LDL-C to the LDL receptor), LDLR, or PCSK9 (gain of
      function); or rarely, identification of biallelic pathogenic variants in
      LDLRAP1.
  - statement: >-
      Management. GeneReviews sets out lipid surveillance from age two years,
      statin initiation in children from around age eight, cardiovascular
      risk-factor modification, and the contraindication of statins in
      pregnancy.
    supporting_text: >-
      Monitor lipid levels from age two years
  - statement: >-
      Agents and circumstances to avoid. GeneReviews names the exposures that
      compound the arterial risk conferred by the receptor defect.
    supporting_text: >-
      Agents/circumstances to avoid: Smoking, high intake of saturated and
      trans unsaturated fat, sedentary lifestyle, obesity, hypertension, and
      diabetes mellitus.
  - statement: >-
      Genetic counseling. GeneReviews states the autosomal dominant
      transmission risk that applies to LDLR-related FH and the more severe,
      earlier-onset presentation of biallelic disease.
    supporting_text: >-
      Each child of an individual with a heterozygous pathogenic variant in
      APOB, LDLR, or PCSK9 has a 50% chance of inheriting the pathogenic
      variant and having FH.
classifications:
  harrisons_chapter:
  - classification_value: ENDOCRINOLOGY_METABOLISM
    evidence:
    - reference: PMID:1301956
      reference_title: "Molecular genetics of the LDL receptor gene in familial hypercholesterolemia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The low density lipoprotein (LDL) receptor is a cell surface transmembrane protein that mediates the uptake and lysosomal degradation of plasma LDL, thereby providing cholesterol to cells."
      explanation: Places the disease in cholesterol/lipoprotein metabolism.
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
    evidence:
    - reference: PMID:1301956
      reference_title: "Molecular genetics of the LDL receptor gene in familial hypercholesterolemia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Mutations disrupting the function of this receptor produce autosomal dominant familial hypercholesterolemia (FH)."
      explanation: Establishes the entity as a Mendelian disorder of a single named gene.
  icimd_category:
  - classification_value: hypercholesterolemias
    evidence:
    - reference: PMID:1301956
      reference_title: "Molecular genetics of the LDL receptor gene in familial hypercholesterolemia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Affected individuals have elevated plasma levels of LDL, which causes premature coronary atherosclerosis."
      explanation: Places LDLR-related FH among the inherited hypercholesterolemias.
inheritance:
- name: Autosomal Dominant
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  penetrance: COMPLETE
  expressivity: VARIABLE
  description: >-
    A single pathogenic LDLR allele is sufficient to raise LDL cholesterol from
    birth, and transmission is autosomal dominant. Penetrance for the
    biochemical phenotype is essentially complete; penetrance for clinical
    cardiovascular events is age-dependent and modified by treatment, Lp(a),
    and conventional risk factors, so expressivity is variable. The trait is
    more precisely co-dominant than dominant, because two pathogenic alleles
    produce a substantially more severe phenotype than one - the gene-dosage
    relation curated under has_subtypes on the umbrella entry.
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "APOB-, LDLR-, and PCSK9-related FH are inherited in an autosomal dominant manner."
    explanation: GeneReviews states the mode of inheritance for LDLR-related FH explicitly.
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Each child of an individual with a heterozygous pathogenic variant in APOB, LDLR, or PCSK9 has a 50% chance of inheriting the pathogenic variant and having FH."
    explanation: States the 50% transmission risk used in genetic counselling.
  - reference: PMID:1301956
    reference_title: "Molecular genetics of the LDL receptor gene in familial hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mutations disrupting the function of this receptor produce autosomal dominant familial hypercholesterolemia (FH)."
    explanation: The founding molecular-genetic account of the disease attributes dominant FH to LDLR mutation.
prevalence:
- population: Molecularly diagnosed familial hypercholesterolemia cohorts
  measure_type: UNKNOWN
  prevalence_class: UNKNOWN
  notes: >-
    Recorded as a share of molecularly solved FH rather than as a population
    rate. LDLR is by a wide margin the most common FH gene, but the reported
    share varies with referral criteria, panel design, and whether
    deletion/duplication analysis was performed, so the figure is carried as a
    quoted range with its source rather than normalized to a single number.
    Population prevalence of the FH phenotype as a whole belongs to the
    umbrella entry (MONDO:0005439) and is not restated here.
  evidence:
  - reference: PMID:30306860
    reference_title: "New Horizons in the Pathogenesis, Pathophysiology and Treatment of Familial Hypercholesterolaemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The most common (60-80%) FH cause is mutations of the LDL Receptor (LDLR) protein (6 classes with a different number of receptors and functionality)."
    explanation: Quantifies the LDLR share of FH and names the receptor-class scheme this entry models.
progression:
- phase: Presymptomatic biochemical disease (birth onward)
  notes: >-
    LDL cholesterol is elevated from birth because the receptor defect is
    constitutional. Heterozygotes are typically asymptomatic through childhood
    while arterial cholesterol exposure accumulates; this is the window in
    which treatment has the largest effect on lifetime risk.
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Monitor lipid levels from age two years"
    explanation: >-
      Surveillance from age two reflects a biochemical phenotype that is
      present long before any clinical event.
- phase: Extravascular cholesterol deposition (childhood to adulthood)
  notes: >-
    Tendon xanthoma, xanthelasma, and premature corneal arcus accumulate with
    age and with the height of the LDL burden. They are specific but
    insensitive - their absence does not exclude the diagnosis.
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Xanthomas (cholesterol deposits in tendons) may be visible in the Achilles tendons or tendons of the hands and worsen with age as a result of extremely high cholesterol levels."
    explanation: Describes the age-dependent accumulation of tendon xanthoma.
- phase: Premature atherosclerotic cardiovascular disease
  notes: >-
    Coronary and proximal aortic plaque develops decades earlier than in the
    general population. In biallelic disease coronary events and calcific
    aortic valve disease can occur in childhood or adolescence.
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Familial hypercholesterolemia (FH) is characterized by significantly elevated low-density
      lipoprotein cholesterol (LDL-C) that leads to atherosclerotic plaque deposition in the
      coronary arteries and proximal aorta at an early age and increases the risk of premature
      cardiovascular events such as angina and myocardial infarction; stroke occurs more rarely. ...
      Individuals with a more severe phenotype, often as a result of biallelic variants, can present
      with very significant elevations in LDL-C (>500 mg/dL), early-onset coronary artery disease
      (CAD; presenting as early as childhood in some), and calcific aortic valve disease. ... The
      molecular diagnosis of FH can be established by identification of heterozygous or biallelic
      pathogenic variants in APOB (variants that impair binding of LDL-C to the LDL receptor), LDLR,
      or PCSK9 (gain of function); or rarely, identification of biallelic pathogenic variants in
      LDLRAP1.
    explanation: >-
      Describes early coronary/proximal aortic atherosclerosis in familial hypercholesterolemia,
      severe biallelic presentation and LDLR among its causes. The excerpt does not quantify the
      decades-earlier comparison.
pathophysiology:
- name: LDLR Loss-of-Function Variant
  role: trigger
  biological_scale: MOLECULAR
  description: >-
    A germline pathogenic variant in LDLR at 19p13.2. The gene spans more than
    45 kb in 18 exons whose boundaries map onto the receptor's functional
    modules - the cysteine-rich ligand-binding repeats, the EGF-precursor
    homology domain, the O-linked sugar domain, the transmembrane segment and
    the cytoplasmic tail - so the mutated exon largely predicts which step of
    the receptor's itinerary is broken. More than 2300 unique FH-associated
    LDLR variants have been catalogued, spanning missense, nonsense,
    frameshift, splice, promoter and exon-level copy-number changes. This node
    is the single lesion; the five nodes immediately downstream are the
    alternative steps at which it can act.
  genes:
  - preferred_term: LDLR
    term:
      id: hgnc:6547
      label: LDLR
  genetic_context:
    gene:
      preferred_term: LDLR
      term:
        id: hgnc:6547
        label: LDLR
    variant_origin: GERMLINE
    functional_impact_category: LOSS_OF_FUNCTION
    description: >-
      The variant consequence is loss of function - fewer functional LDL
      receptors reach or persist on the hepatocyte surface. Recorded on the
      genetic context rather than as a Descriptor modifier because the claim is
      about the consequence of an allele. The severity of that loss is
      allele-specific and is the subject of the class nodes downstream.
  molecular_functions:
  - preferred_term: low-density lipoprotein particle receptor activity
    modifier: DECREASED
    term:
      id: GO:0005041
      label: low-density lipoprotein particle receptor activity
  locations:
  - preferred_term: liver
    term:
      id: UBERON:0002107
      label: liver
  evidence:
  - reference: PMID:1301956
    reference_title: "Molecular genetics of the LDL receptor gene in familial hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mutations disrupting the function of this receptor produce autosomal dominant familial hypercholesterolemia (FH)."
    explanation: States the causal relation that defines this entry's trigger node.
  - reference: PMID:2988123
    reference_title: "The LDL receptor gene: a mosaic of exons shared with different proteins."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "This gene is more than 45 kilobases in length and contains 18 exons, most of which correlate with functional domains previously defined at the protein level."
    explanation: >-
      Establishes the exon-to-domain correspondence that underlies the
      structure-function mapping used by the class nodes downstream.
  - reference: PMID:34906454
    reference_title: "The Clinical Genome Resource (ClinGen) Familial Hypercholesterolemia Variant Curation Expert Panel consensus guidelines for LDLR variant classification."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In this study, we provide consensus recommendations for the most common FH-associated gene, LDLR, where >2300 unique FH-associated variants have been identified."
    explanation: Quantifies the size of the LDLR allelic series curated by this entry.
  downstream:
  - target: Absent LDL Receptor Synthesis
    causal_link_type: DIRECT
    description: >-
      Null (class 1) alleles - large deletions removing the promoter, nonsense
      and frameshift changes, and alleles producing no detectable protein -
      abolish receptor synthesis outright.
    evidence:
    - reference: PMID:3343347
      reference_title: "Multiple crm- mutations in familial hypercholesterolemia. Evidence for 13 alleles, including four deletions."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "16 of the 132 cell strains (12%) synthesized no immunodetectable LDL receptor protein, indicating the presence of two mutant genes that failed to produce cross-reacting material (crm- mutations)."
      explanation: >-
        Demonstrates the null class directly - patient fibroblasts making no
        detectable receptor protein at all.
  - target: Impaired ER-to-Golgi Transport of the LDL Receptor
    causal_link_type: DIRECT
    description: >-
      Class 2 alleles allow synthesis but the receptor misfolds and is retained
      in the endoplasmic reticulum instead of maturing through the Golgi.
    evidence:
    - reference: PMID:32015373
      reference_title: "Mutation type classification and pathogenicity assignment of sixteen missense variants located in the EGF-precursor homology domain of the LDLR."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Of the analysed variants, we found six non-pathogenic LDLR variants and ten pathogenic variants distributed as follow: three class 3 variants; four class 2 variants; and three class 5 variants."
      explanation: >-
        Assigns real patient variants to the transport-defective class in a
        functional assay, showing the class is an operational category and not
        just a textbook scheme.
  - target: Defective LDL Binding at the Hepatocyte Surface
    causal_link_type: DIRECT
    description: >-
      Class 3 alleles produce a receptor that reaches the surface but binds
      apoB-100 poorly, typically through changes in the cysteine-rich
      ligand-binding repeats or in the EGF-precursor domain that positions
      them.
    evidence:
    - reference: PMID:32015373
      reference_title: "Mutation type classification and pathogenicity assignment of sixteen missense variants located in the EGF-precursor homology domain of the LDLR."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "The activity of sixteen LDLR variants was functionally characterized by determining LDLR expression by Western blot and LDLR expression, LDL binding capacity and uptake, and LDLR recycling activity by flow cytometry in transfected CHO-ldlA7 cells."
      explanation: >-
        Describes the assay that separates a binding defect from expression and
        recycling defects, which is what makes this a distinct node.
  - target: Defective Clustering in Clathrin-Coated Pits
    causal_link_type: DIRECT
    description: >-
      Class 4 alleles disable the cytoplasmic internalization signal, so a
      fully synthesized, surface-expressed, ligand-competent receptor never
      enters the cell.
    evidence:
    - reference: PMID:3955657
      reference_title: "The J.D. mutation in familial hypercholesterolemia: amino acid substitution in cytoplasmic domain impedes internalization of LDL receptors."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "The DNA sequence revealed a substitution of a cysteine codon for a tyrosine codon at residue 807 in the cytoplasmic domain of the receptor."
      explanation: >-
        Identifies the founding internalization-defective allele and localizes
        it to the cytoplasmic tail rather than the ligand-binding region.
  - target: Defective Endosomal Ligand Release and Receptor Recycling
    causal_link_type: DIRECT
    description: >-
      Class 5 alleles allow binding and internalization but the receptor fails
      to release LDL in the acidified endosome, so receptor and ligand are
      degraded together instead of the receptor returning to the surface.
    evidence:
    - reference: PMID:32015373
      reference_title: "Mutation type classification and pathogenicity assignment of sixteen missense variants located in the EGF-precursor homology domain of the LDLR."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "LDLR structure is organized in 5 different domains, including an EGF-precursor homology domain that plays a pivotal role in lipoprotein release and receptor recycling."
      explanation: >-
        Assigns the ligand-release and recycling step to a specific receptor
        domain, the structural basis of the class 5 phenotype.
- name: Absent LDL Receptor Synthesis
  biological_scale: MOLECULAR
  description: >-
    The class 1 (null, receptor-negative) branch. No immunodetectable LDL
    receptor protein is made, because the allele deletes the promoter, produces
    no mRNA, or produces mRNA that yields no protein. This is the most severe
    branch and the one with the least therapeutic room: there is no receptor to
    upregulate. In clinical trials of homozygous disease it is operationalized
    as "null-null" or receptor-negative status.
  cell_types:
  - preferred_term: hepatocyte
    term:
      id: CL:0000182
      label: hepatocyte
  molecular_functions:
  - preferred_term: low-density lipoprotein particle receptor activity
    modifier: ABSENT
    term:
      id: GO:0005041
      label: low-density lipoprotein particle receptor activity
  evidence:
  - reference: PMID:3343347
    reference_title: "Multiple crm- mutations in familial hypercholesterolemia. Evidence for 13 alleles, including four deletions."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Four of the alleles produced no mRNA. Three of these four mRNA- alleles had large deletions ranging from 6 to 20 kb that eliminated the promoter region of the gene."
    explanation: Documents the molecular routes to complete absence of receptor protein.
  - reference: PMID:32813947
    reference_title: "Evinacumab for Homozygous Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This disorder is associated with genetic variants that result in virtually absent (null-null) or impaired (non-null) LDL-receptor activity."
    explanation: >-
      Shows the null versus non-null distinction being used as a formal
      stratifier in a contemporary phase 3 trial.
  downstream:
  - target: Reduced Functional Hepatic LDL Receptor Activity
    causal_link_type: DIRECT
    description: Absent receptor protein is the limiting case of reduced receptor activity.
    evidence:
    - reference: PMID:3343347
      reference_title: "Multiple crm- mutations in familial hypercholesterolemia. Evidence for 13 alleles, including four deletions."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "16 of the 132 cell strains (12%) synthesized no immunodetectable LDL receptor protein, indicating the presence of two mutant genes that failed to produce cross-reacting material (crm- mutations)."
      explanation: >-
        Reports the measured result: in 12% of homozygous FH cell strains no
        receptor protein is made at all, which is the limiting case of reduced
        receptor activity this edge asserts.
- name: Impaired ER-to-Golgi Transport of the LDL Receptor
  biological_scale: MOLECULAR
  description: >-
    The class 2 (transport-defective) branch. The receptor is synthesized but
    misfolds and is retained in the endoplasmic reticulum rather than being
    further glycosylated in the Golgi and delivered to the surface. Retention
    may be complete (class 2a) or partial (class 2b), and partial retention
    leaves residual surface receptor - which matters therapeutically, because
    residual receptor is what receptor-directed drugs act on.
  cell_types:
  - preferred_term: hepatocyte
    term:
      id: CL:0000182
      label: hepatocyte
  biological_processes:
  - preferred_term: endoplasmic reticulum to Golgi vesicle-mediated transport
    modifier: DECREASED
    term:
      id: GO:0006888
      label: endoplasmic reticulum to Golgi vesicle-mediated transport
  evidence:
  - reference: PMID:32015373
    reference_title: "Mutation type classification and pathogenicity assignment of sixteen missense variants located in the EGF-precursor homology domain of the LDLR."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Of the analysed variants, we found six non-pathogenic LDLR variants and ten pathogenic variants distributed as follow: three class 3 variants; four class 2 variants; and three class 5 variants."
    explanation: Assigns patient variants to the transport-defective class by functional assay.
  - reference: PMID:25386756
    reference_title: "Advantages and versatility of fluorescence-based methodology to characterize the functionality of LDLR and class mutation assignment."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Additionally confocal microscopy allowed the assignment of different class mutation to the variants assayed."
    explanation: >-
      Confirms that subcellular localization imaging is what distinguishes an
      ER-retained receptor from a surface-expressed one.
  downstream:
  - target: Reduced Functional Hepatic LDL Receptor Activity
    causal_link_type: DIRECT
    description: >-
      A receptor stuck in the ER never reaches the surface, so it contributes
      nothing to LDL clearance regardless of whether its ligand-binding
      sequence is intact.
    evidence:
    - reference: PMID:25386756
      reference_title: "Advantages and versatility of fluorescence-based methodology to characterize the functionality of LDLR and class mutation assignment."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Use of fluorescence yielded similar results than 125I-labeled lipoproteins concerning LDLR activity determination, and also allows class mutation classification."
      explanation: >-
        Reports that a single functional readout - LDLR activity - both
        reproduces the reference radiolabel measurement and resolves which
        mutation class produced it, which is what makes receptor activity the
        common quantity every class converges on.
- name: Defective LDL Binding at the Hepatocyte Surface
  biological_scale: MOLECULAR
  description: >-
    The class 3 (binding-defective) branch. Receptor reaches the surface in
    normal numbers but binds apoB-100-containing LDL with reduced affinity.
    Changes typically fall in the cysteine-rich ligand-binding repeats or in the
    EGF-precursor homology domain that holds them in a binding-competent
    conformation. This is the receptor-side mirror of the ligand-side defect
    curated in Familial_Defective_Apolipoprotein_B-100 - the same handshake
    fails, from the other side.
  cell_types:
  - preferred_term: hepatocyte
    term:
      id: CL:0000182
      label: hepatocyte
  genes:
  - preferred_term: LDLR
    term:
      id: hgnc:6547
      label: LDLR
  molecular_functions:
  - preferred_term: low-density lipoprotein particle binding
    modifier: DECREASED
    term:
      id: GO:0030169
      label: low-density lipoprotein particle binding
  evidence:
  - reference: PMID:32015373
    reference_title: "Mutation type classification and pathogenicity assignment of sixteen missense variants located in the EGF-precursor homology domain of the LDLR."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "They showed similar expression to wt LDLR but demonstrated deficient LDL binding."
    explanation: >-
      The defining functional signature of the class 3 branch: receptor is
      expressed at normal levels yet binds LDL poorly, separating a binding
      defect from a synthesis or trafficking defect.
  - reference: PMID:31106925
    reference_title: "Functional analysis of new variants at the low-density lipoprotein receptor associated with familial hypercholesterolemia."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "All new LDLR variants found in our patients were functionally validated in CHO-ldlA7 cells. The LDLR activity was measured by flow cytometry and LDLR expression was detected by immunofluorescence."
    explanation: >-
      Describes the paired activity/expression measurement that identifies a
      binding defect - normal expression with reduced activity.
  downstream:
  - target: Reduced Functional Hepatic LDL Receptor Activity
    causal_link_type: DIRECT
    description: >-
      A surface receptor that cannot capture its ligand removes no LDL, so
      functional receptor activity falls even though receptor abundance is
      normal.
    evidence:
    - reference: PMID:31106925
      reference_title: "Functional analysis of new variants at the low-density lipoprotein receptor associated with familial hypercholesterolemia."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "The functional in vitro characterization of rare variants at the LDLR is a useful tool to classify the new variants."
      explanation: >-
        Establishes measured receptor function, not receptor presence, as the
        quantity that classifies an allele.
- name: Defective Clustering in Clathrin-Coated Pits
  biological_scale: CELLULAR
  description: >-
    The class 4 (internalization-defective) branch. The cytoplasmic tail of the
    LDL receptor carries the signal that concentrates it in clathrin-coated
    pits; a change there leaves a receptor that is expressed and binds LDL
    normally but is distributed diffusely over the surface and enters the cell
    slowly. The founding example is patient J.D., whose receptor carries a
    tyrosine-to-cysteine substitution at residue 807. Because the LDLRAP1/ARH
    adaptor serves this same step, the recessive LDLRAP1 disease is the
    phenocopy of this branch acting in trans.
  cell_types:
  - preferred_term: hepatocyte
    term:
      id: CL:0000182
      label: hepatocyte
  biological_processes:
  - preferred_term: clathrin-dependent endocytosis
    modifier: DECREASED
    term:
      id: GO:0072583
      label: clathrin-dependent endocytosis
  evidence:
  - reference: PMID:3955657
    reference_title: "The J.D. mutation in familial hypercholesterolemia: amino acid substitution in cytoplasmic domain impedes internalization of LDL receptors."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Upon transfection into receptor-deficient hamster cells, the cDNA specified a receptor that bound LDL normally, but entered the cell slowly."
    explanation: >-
      Separates binding from internalization experimentally - the defining
      observation for this class.
  - reference: PMID:3955657
    reference_title: "The J.D. mutation in familial hypercholesterolemia: amino acid substitution in cytoplasmic domain impedes internalization of LDL receptors."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Electron microscopy showed that this receptor was distributed diffusely over the cell surface, whereas the receptor produced by the normal cDNA was concentrated in coated pits."
    explanation: >-
      Direct morphological evidence that the lesion is failure to cluster in
      clathrin-coated pits.
  downstream:
  - target: Reduced Functional Hepatic LDL Receptor Activity
    causal_link_type: DIRECT
    description: >-
      A receptor that binds LDL but does not internalize it does not clear it;
      the bound particle is not delivered to the lysosome.
    evidence:
    - reference: PMID:3955657
      reference_title: "The J.D. mutation in familial hypercholesterolemia: amino acid substitution in cytoplasmic domain impedes internalization of LDL receptors."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "These results support the hypothesis that cytoplasmic domains direct receptors to coated pits, thereby determining the high rate of receptor internalization in animal cells."
      explanation: >-
        States the general principle - internalization rate, and therefore
        clearance capacity, is set by the cytoplasmic signal.
- name: Defective Endosomal Ligand Release and Receptor Recycling
  biological_scale: CELLULAR
  description: >-
    The class 5 (recycling-defective) branch. Binding and internalization are
    intact, but the receptor fails to release LDL when the endosome acidifies,
    so receptor and ligand traffic together to the lysosome and the receptor is
    consumed rather than returned to the surface. Each receptor therefore makes
    one round trip instead of many, and functional clearance capacity collapses
    even though synthesis is normal. This is also the step that PCSK9 subverts
    pharmacologically, which is why PCSK9-directed drugs raise receptor
    abundance in patients who still have recyclable receptor.
  cell_types:
  - preferred_term: hepatocyte
    term:
      id: CL:0000182
      label: hepatocyte
  biological_processes:
  - preferred_term: receptor recycling
    modifier: DECREASED
    term:
      id: GO:0001881
      label: receptor recycling
  evidence:
  - reference: PMID:32015373
    reference_title: "Mutation type classification and pathogenicity assignment of sixteen missense variants located in the EGF-precursor homology domain of the LDLR."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "LDLR structure is organized in 5 different domains, including an EGF-precursor homology domain that plays a pivotal role in lipoprotein release and receptor recycling."
    explanation: Localizes ligand release and recycling to a specific receptor domain.
  - reference: PMID:32015373
    reference_title: "Mutation type classification and pathogenicity assignment of sixteen missense variants located in the EGF-precursor homology domain of the LDLR."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "In this way, although the protein structure is not affected in LDLR expression or LDL binding and uptake activities, the alteration introduced by the asparagine is enough to cause a defect in recycling of the protein."
    explanation: >-
      Isolates the class 5 defect: expression, binding and uptake are all
      intact and recycling alone fails, which is what distinguishes this branch
      from the synthesis, trafficking and binding branches.
  downstream:
  - target: Reduced Functional Hepatic LDL Receptor Activity
    causal_link_type: DIRECT
    description: >-
      Loss of recycling converts a reusable receptor into a single-use one,
      cutting the LDL particles cleared per receptor synthesized.
    evidence:
    - reference: PMID:32015373
      reference_title: "Mutation type classification and pathogenicity assignment of sixteen missense variants located in the EGF-precursor homology domain of the LDLR."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "These results can be incorporated into clinical management of patients by helping guide the appropriate level of treatment intensity depending on the extent of loss of LDLR activity."
      explanation: >-
        States explicitly that class assignment resolves into a single quantity
        - extent of loss of LDLR activity - which is this convergence node.
- name: Reduced Functional Hepatic LDL Receptor Activity
  role: central_effector
  biological_scale: CELLULAR
  description: >-
    The convergence node of the allelic series. Whichever step is broken -
    synthesis, ER export, ligand binding, internalization, or recycling - the
    measurable output is the same: fewer LDL particles cleared per unit time by
    the hepatocyte. Functional assays report this as a single quantity
    (percentage of wild-type LDL uptake), which is why class assignment and
    residual activity are recorded separately: the class says *where* the
    itinerary breaks, the residual activity says *how much* capacity survives.
    Null alleles are conventionally under about 2% of normal activity, though
    trial protocols have operationalized "null" at thresholds as high as 15%.
  cell_types:
  - preferred_term: hepatocyte
    term:
      id: CL:0000182
      label: hepatocyte
  biological_processes:
  - preferred_term: receptor-mediated endocytosis
    modifier: DECREASED
    term:
      id: GO:0006898
      label: receptor-mediated endocytosis
  molecular_functions:
  - preferred_term: low-density lipoprotein particle receptor activity
    modifier: DECREASED
    term:
      id: GO:0005041
      label: low-density lipoprotein particle receptor activity
  locations:
  - preferred_term: liver
    term:
      id: UBERON:0002107
      label: liver
  evidence:
  - reference: PMID:1301956
    reference_title: "Molecular genetics of the LDL receptor gene in familial hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The low density lipoprotein (LDL) receptor is a cell surface transmembrane protein that mediates the uptake and lysosomal degradation of plasma LDL, thereby providing cholesterol to cells."
    explanation: States the receptor function whose reduction this node represents.
  - reference: PMID:32015373
    reference_title: "Mutation type classification and pathogenicity assignment of sixteen missense variants located in the EGF-precursor homology domain of the LDLR."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "These results can be incorporated into clinical management of patients by helping guide the appropriate level of treatment intensity depending on the extent of loss of LDLR activity."
    explanation: >-
      Treats residual LDLR activity as the single clinically actionable output
      of the allelic series.
  downstream:
  - target: Impaired Receptor-Mediated Clearance of Plasma LDL
    causal_link_type: DIRECT
    description: >-
      Hepatic LDL receptors perform most clearance of circulating LDL, so a
      fall in functional receptor activity directly lengthens LDL residence
      time in plasma.
    evidence:
    - reference: PMID:8349823
      reference_title: "Hypercholesterolemia in low density lipoprotein receptor knockout mice and its reversal by adenovirus-mediated gene delivery."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "The half-lives for intravenously administered 125I-VLDL and 125I-LDL were prolonged by 30-fold and 2.5-fold, respectively, but the clearance of 125I-HDL was normal in the LDLR-/- mice."
      explanation: >-
        Measures the clearance defect directly, and shows it is specific to
        apoB-containing particles.
  - target: Residual Receptor Activity Gates Receptor-Dependent LDL Lowering
    causal_link_type: DIRECT
    description: >-
      The same residual activity that sets the untreated LDL level also sets
      how much a receptor-directed drug can achieve, because those drugs act by
      increasing the number of functional receptors rather than by creating
      them.
    evidence:
    - reference: PMID:24014831
      reference_title: "Effect of the proprotein convertase subtilisin/kexin 9 monoclonal antibody, AMG 145, in homozygous familial hypercholesterolemia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "This study demonstrates significant and dose-related LDL cholesterol lowering with a PCSK9 monoclonal antibody in homozygous familial hypercholesterolemia patients with defective LDL receptor activity but no reduction in those who were receptor negative."
      explanation: >-
        Direct clinical demonstration that residual receptor activity, not
        drug dose, determines whether a receptor-directed therapy works.
- name: Residual Receptor Activity Gates Receptor-Dependent LDL Lowering
  biological_scale: ORGANISM
  description: >-
    The pharmacogenetic node, and the reason the allelic series is clinically
    actionable rather than merely descriptive. Statins lower intracellular
    cholesterol and thereby induce more LDL receptor; PCSK9 antibodies and
    inclisiran prevent or reduce PCSK9-mediated receptor degradation. Both
    families of drugs work by putting *more* receptor on the hepatocyte
    surface, so both require a receptor that can be made and can function. The
    genotype-stratified evidence below is for a PCSK9 antibody: in the two
    receptor-negative (null-null) homozygotes studied there was nothing to
    induce and the response was absent, while in receptor-defective
    homozygotes there was residual receptor and the response was preserved.
    Whether statins behave the same way in receptor-negative disease has not
    been tested here - the two null patients in that trial were already on
    stable statin therapy at enrolment - and the mechanisms differ (statins act
    transcriptionally on receptor synthesis, PCSK9-directed agents
    post-translationally on receptor degradation and recycling), so the
    statin/PCSK9 asymmetry is carried as an open question in the
    residual_ldlr_activity_response_threshold discussion rather than asserted.
    LDLR-independent agents - the MTP inhibitor lomitapide, the ANGPTL3
    antibody evinacumab, and lipoprotein apheresis - bypass the receptor
    entirely and retain effect in null-null disease. This node is the target of
    the treatment entries curated below.
  cell_types:
  - preferred_term: hepatocyte
    term:
      id: CL:0000182
      label: hepatocyte
  locations:
  - preferred_term: liver
    term:
      id: UBERON:0002107
      label: liver
  evidence:
  - reference: PMID:24014831
    reference_title: "Effect of the proprotein convertase subtilisin/kexin 9 monoclonal antibody, AMG 145, in homozygous familial hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "No reduction was seen in the 2 receptor-negative patients."
    explanation: >-
      The negative half of the relation - a receptor-directed drug does nothing
      when no receptor can be made.
  - reference: PMID:24014831
    reference_title: "Effect of the proprotein convertase subtilisin/kexin 9 monoclonal antibody, AMG 145, in homozygous familial hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Over the treatment periods, mean±SD LDL cholesterol reductions in the 6 LDL receptor-defective patients were 19.3±16% and 26.3±20% with 4- and 2-week dosing, respectively"
    explanation: >-
      The positive half - the same drug in the same trial lowers LDL when
      residual receptor activity exists.
  - reference: PMID:32813947
    reference_title: "Evinacumab for Homozygous Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The LDL cholesterol level was lower in the evinacumab group than in the placebo group in patients with null-null variants (-43.4% vs. +16.2%) and in those with non-null variants (-49.1% vs. -3.8%)."
    explanation: >-
      Shows the complementary case - an LDLR-independent mechanism works in
      both genotype strata, which is what makes the gating relation
      therapeutically consequential rather than merely prognostic.
  notes: >-
    Caveat on strength of claim: the receptor-negative arm of the AMG 145 study
    comprised two patients, so "no response in receptor-negative disease" rests
    on a very small n even though it is consistent with the mechanism and with
    the way regulatory labels and trial protocols stratify HoFH. Treat the
    direction as well supported and the magnitude as imprecise.
- name: Impaired Receptor-Mediated Clearance of Plasma LDL
  biological_scale: ORGANISM
  description: >-
    Reduced hepatic receptor capacity lengthens the residence time of
    apoB-100-containing LDL and IDL in plasma. The defect is specific to the
    receptor's ligands: HDL clearance is unaffected, which is why the
    biochemical phenotype is an isolated elevation of LDL rather than a
    generalized dyslipidemia.
  biological_processes:
  - preferred_term: low-density lipoprotein particle clearance
    modifier: DECREASED
    term:
      id: GO:0034383
      label: low-density lipoprotein particle clearance
  locations:
  - preferred_term: liver
    term:
      id: UBERON:0002107
      label: liver
  evidence:
  - reference: PMID:8183926
    reference_title: "The two-receptor model of lipoprotein clearance: tests of the hypothesis in \"knockout\" mice lacking the low density lipoprotein receptor, apolipoprotein E, or both proteins."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "LDLR(-/-) mice had a relatively isolated elevation in plasma LDL"
    explanation: >-
      Shows that loss of the receptor produces a selective LDL clearance
      defect rather than a global lipoprotein abnormality.
  - reference: PMID:8349823
    reference_title: "Hypercholesterolemia in low density lipoprotein receptor knockout mice and its reversal by adenovirus-mediated gene delivery."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "We conclude that the LDL receptor is responsible in part for the low levels of VLDL, IDL, and LDL in wild-type mice"
    explanation: Attributes normal plasma LDL levels to receptor-mediated clearance.
  downstream:
  - target: Lifelong Elevation of Plasma LDL Cholesterol
    causal_link_type: DIRECT
    description: >-
      Reduced clearance against unchanged production raises the steady-state
      plasma LDL concentration, from birth and for life.
    evidence:
    - reference: PMID:8349823
      reference_title: "Hypercholesterolemia in low density lipoprotein receptor knockout mice and its reversal by adenovirus-mediated gene delivery."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Total plasma cholesterol levels were twofold higher than those of wild-type litter-mates, owing to a seven- to ninefold increase in intermediate density lipoproteins (IDL) and LDL without a significant change in HDL."
      explanation: >-
        Quantifies the rise in plasma IDL/LDL that follows loss of receptor
        clearance capacity.
- name: Lifelong Elevation of Plasma LDL Cholesterol
  biological_scale: ORGANISM
  description: >-
    The defining biochemical phenotype. Because the receptor defect is
    constitutional, LDL cholesterol is elevated from birth, so the arterial
    tree accumulates cholesterol exposure over decades rather than from midlife
    onward. Untreated heterozygotes typically exceed 190 mg/dL; biallelic
    disease often exceeds 400-500 mg/dL.
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A clinical diagnosis of FH can be established in a proband with characteristic clinical features and significantly elevated LDL-C levels (typically >190 mg/dL in adults and >160 mg/dL in children)."
    explanation: Gives the diagnostic LDL-C thresholds for the untreated phenotype.
  - reference: PMID:37130090
    reference_title: "2023 Update on European Atherosclerosis Society Consensus Statement on Homozygous Familial Hypercholesterolaemia: new treatments and clinical guidance."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a low-density lipoprotein cholesterol (LDL-C) >10 mmol/L (>400 mg/dL) is suggestive of HoFH and warrants further evaluation"
    explanation: Gives the biallelic-disease threshold used in current consensus guidance.
  downstream:
  - target: Endothelial Dysfunction and Subendothelial LDL Retention
    causal_link_type: DIRECT
    description: >-
      Sustained high plasma LDL drives entry of apoB particles into the
      arterial intima and their retention on subendothelial proteoglycan - the
      initiating step of the shared atherogenesis programme.
    evidence:
    - reference: PMID:24404629
      reference_title: "Familial Hypercholesterolemia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Familial hypercholesterolemia (FH) is characterized by significantly elevated low-density lipoprotein cholesterol (LDL-C) that leads to atherosclerotic plaque deposition in the coronary arteries and proximal aorta at an early age"
      explanation: States the LDL-to-plaque relation and its predilection sites.
  - target: Extravascular Cholesterol Deposition in Tendon, Skin, and Cornea
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - uptake of excess LDL-derived cholesterol by tissue macrophages
    description: >-
      The same circulating excess deposits outside the arterial wall, producing
      the classical stigmata. These are specific but insensitive, and are less
      often seen now that treatment begins earlier.
    evidence:
    - reference: PMID:24404629
      reference_title: "Familial Hypercholesterolemia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Xanthomas (cholesterol deposits in tendons) may be visible in the Achilles tendons or tendons of the hands and worsen with age as a result of extremely high cholesterol levels."
      explanation: >-
        Attributes tendon xanthoma directly to cholesterol deposition driven by
        the height of the circulating burden.
- name: Endothelial Dysfunction and Subendothelial LDL Retention
  biological_scale: TISSUE
  conforms_to: "atherogenesis#Endothelial Dysfunction and Subendothelial LDL Retention"
  description: >-
    Conformance node. The atherogenic cascade downstream of the LDL elevation
    is the conserved one modelled in the atherogenesis module and is not
    re-derived here; what is disease-specific is that the apoB-lipoprotein
    driver is present from birth and at several times the usual concentration,
    so the same programme runs decades earlier.
  cell_types:
  - preferred_term: endothelial cell of artery
    term:
      id: CL:1000413
      label: endothelial cell of artery
  locations:
  - preferred_term: artery
    term:
      id: UBERON:0001637
      label: artery
  evidence:
  - reference: PMID:31748469
    reference_title: "The History of the WHHL Rabbit, an Animal Model of Familial Hypercholesterolemia (I) - Contribution to the Elucidation of the Pathophysiology of Human Hypercholesterolemia and Coronary Heart Disease."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Oxidized LDL accumulates in the arterial wall, monocyte adhesion molecules are expressed on arterial endothelial cells, and monocyte-derived macrophages infiltrate the arterial intima, resulting in the formation and progression of atherosclerosis."
    explanation: >-
      Describes the initiating arterial events as established in the
      LDLR-deficient rabbit, the model in which they were demonstrated in vivo.
  downstream:
  - target: Monocyte Recruitment and Macrophage Foam Cell Formation
    causal_link_type: DIRECT
    description: Retained and modified LDL recruits monocytes that become lipid-laden macrophages.
    evidence:
    - reference: PMID:31748469
      reference_title: "The History of the WHHL Rabbit, an Animal Model of Familial Hypercholesterolemia (I) - Contribution to the Elucidation of the Pathophysiology of Human Hypercholesterolemia and Coronary Heart Disease."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "monocyte adhesion molecules are expressed on arterial endothelial cells, and monocyte-derived macrophages infiltrate the arterial intima"
      explanation: Links endothelial activation to monocyte recruitment in the LDLR-deficient rabbit.
- name: Monocyte Recruitment and Macrophage Foam Cell Formation
  biological_scale: TISSUE
  conforms_to: "atherogenesis#Monocyte Recruitment and Macrophage Foam Cell Formation"
  description: >-
    Conformance node. Recruited monocyte-derived macrophages take up modified
    LDL and become foam cells, the cellular substance of the early lesion.
  cell_types:
  - preferred_term: macrophage
    term:
      id: CL:0000235
      label: macrophage
  - preferred_term: foam cell
    term:
      id: CL:0000891
      label: foam cell
  locations:
  - preferred_term: artery
    term:
      id: UBERON:0001637
      label: artery
  evidence:
  - reference: PMID:31748469
    reference_title: "The History of the WHHL Rabbit, an Animal Model of Familial Hypercholesterolemia (I) - Contribution to the Elucidation of the Pathophysiology of Human Hypercholesterolemia and Coronary Heart Disease."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "monocyte-derived macrophages infiltrate the arterial intima, resulting in the formation and progression of atherosclerosis"
    explanation: States macrophage infiltration as the step that builds the lesion.
  downstream:
  - target: Premature Atherosclerotic Cardiovascular Events
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - fibrofatty plaque growth and necrotic core formation
    - plaque instability and rupture
    - occlusive thrombosis
    description: >-
      Lesion growth, destabilization and thrombosis convert subclinical plaque
      into clinical events; the intervening steps are the conserved ones in the
      atherogenesis module.
    evidence:
    - reference: PMID:31748469
      reference_title: "The History of the WHHL Rabbit, an Animal Model of Familial Hypercholesterolemia (I) - Contribution to the Elucidation of the Pathophysiology of Human Hypercholesterolemia and Coronary Heart Disease."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "The rupture of coronary lesions requires secondary mechanical forces, such as spasm, in addition to vulnerable plaques."
      explanation: >-
        Identifies plaque rupture as the step between lesion and event, and
        notes it is not determined by plaque composition alone.
- name: Premature Atherosclerotic Cardiovascular Events
  biological_scale: ORGANISM
  conforms_to: "atherogenesis#Plaque Rupture, Thrombosis, and Ischemic Events"
  description: >-
    Conformance node. Angina, myocardial infarction, and less often stroke,
    occurring decades earlier than in the general population. In biallelic
    disease events may occur in childhood or adolescence and are accompanied by
    calcific aortic valve and aortic root disease, which is a supravalvular
    rather than purely valvular lesion and is not prevented by LDL lowering as
    reliably as coronary events are.
  locations:
  - preferred_term: coronary artery
    term:
      id: UBERON:0001621
      label: coronary artery
  - preferred_term: aortic valve
    term:
      id: UBERON:0002137
      label: aortic valve
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "increases the risk of premature cardiovascular events such as angina and myocardial infarction; stroke occurs more rarely"
    explanation: Names the clinical events and their relative frequency.
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Individuals with a more severe phenotype, often as a result of biallelic variants, can present with very significant elevations in LDL-C (>500 mg/dL), early-onset coronary artery disease (CAD; presenting as early as childhood in some), and calcific aortic valve disease."
    explanation: Establishes the childhood-onset and aortic valve arms in biallelic disease.
- name: Extravascular Cholesterol Deposition in Tendon, Skin, and Cornea
  biological_scale: TISSUE
  description: >-
    Macrophage-mediated deposition of LDL-derived cholesterol outside the
    arterial wall, producing tendon xanthoma (Achilles and extensor tendons of
    the hands), xanthelasma at the eyelids, and premature corneal arcus. These
    signs are highly specific for the untreated phenotype and are used in the
    Dutch Lipid Clinic Network and Simon Broome criteria, but they are
    insensitive - absence does not exclude the diagnosis, and early treatment
    both prevents and can reverse them.
  cell_types:
  - preferred_term: macrophage
    term:
      id: CL:0000235
      label: macrophage
  locations:
  - preferred_term: tendon
    term:
      id: UBERON:0000043
      label: tendon
  - preferred_term: cornea
    term:
      id: UBERON:0000964
      label: cornea
  - preferred_term: eyelid
    term:
      id: UBERON:0001711
      label: eyelid
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Xanthelasmas (yellowish, waxy deposits) can occur around the eyelids."
    explanation: Documents the periocular deposition site.
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Individuals with FH may develop corneal arcus (white, gray, or blue opaque ring in the corneal margin as a result of cholesterol deposition) at a younger age than those without FH."
    explanation: Documents corneal deposition and its premature timing.
  - reference: PMID:37730951
    reference_title: "Generation of a familial hypercholesterolemia model in non-human primate."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "In addition, periocular xanthoma was observed only 1 year after birth."
    explanation: >-
      Independent demonstration in an LDLR-knockout primate that removing the
      receptor alone is sufficient to produce periocular xanthoma.
phenotypes:
- category: Biochemical
  name: Hypercholesterolemia
  description: >-
    Elevated total cholesterol from birth, driven entirely by the LDL fraction.
  phenotype_term:
    preferred_term: Hypercholesterolemia
    term:
      id: HP:0003124
      label: Hypercholesterolemia
    temporality: CHRONIC
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:1301956
    reference_title: "Molecular genetics of the LDL receptor gene in familial hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected individuals have elevated plasma levels of LDL, which causes premature coronary atherosclerosis."
    explanation: States the defining biochemical abnormality of LDLR-mutation carriers.
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Familial hypercholesterolemia (FH) is characterized by significantly elevated low-density lipoprotein cholesterol (LDL-C)"
    explanation: >-
      GeneReviews states the elevation as the characterizing feature. Frequency
      is set VERY_FREQUENT because the biochemical phenotype is essentially
      fully penetrant in variant carriers.
- category: Biochemical
  name: Elevated LDL Cholesterol
  description: >-
    The measured abnormality used for diagnosis and for monitoring treatment.
    Typically above 190 mg/dL in untreated adult heterozygotes and above 400
    mg/dL in biallelic disease.
  phenotype_term:
    preferred_term: Increased LDL cholesterol concentration
    term:
      id: HP:0003141
      label: Increased LDL cholesterol concentration
    temporality: CHRONIC
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A clinical diagnosis of FH can be established in a proband with characteristic clinical features and significantly elevated LDL-C levels (typically >190 mg/dL in adults and >160 mg/dL in children)."
    explanation: Gives the diagnostic thresholds and establishes the phenotype's universality.
  - reference: PMID:37130090
    reference_title: "2023 Update on European Atherosclerosis Society Consensus Statement on Homozygous Familial Hypercholesterolaemia: new treatments and clinical guidance."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a low-density lipoprotein cholesterol (LDL-C) >10 mmol/L (>400 mg/dL) is suggestive of HoFH and warrants further evaluation"
    explanation: Gives the corresponding threshold in biallelic disease.
- category: Physical
  name: Tendon Xanthoma
  description: >-
    Cholesterol deposits in the Achilles tendons and the extensor tendons of
    the hands, accumulating with age and with the magnitude of the LDL burden.
    Specific but insensitive.
  phenotype_term:
    preferred_term: Tendon xanthomatosis
    term:
      id: HP:0010874
      label: Tendon xanthomatosis
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Xanthomas (cholesterol deposits in tendons) may be visible in the Achilles tendons or tendons of the hands and worsen with age as a result of extremely high cholesterol levels."
    explanation: >-
      Names the sites and the progressive course. Frequency is deliberately
      omitted - reported prevalence varies widely with treatment era and
      ascertainment, and no quotable figure specific to LDLR-related FH was
      available.
- category: Physical
  name: Xanthelasma
  description: Yellowish waxy cholesterol deposits around the eyelids.
  phenotype_term:
    preferred_term: Xanthelasma
    term:
      id: HP:0001114
      label: Xanthelasma
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Xanthelasmas (yellowish, waxy deposits) can occur around the eyelids."
    explanation: Documents the sign and its location.
- category: Physical
  name: Premature Corneal Arcus
  description: >-
    An opaque ring at the corneal margin from cholesterol deposition, appearing
    at a younger age than the age-related form.
  phenotype_term:
    preferred_term: Corneal arcus
    term:
      id: HP:0001084
      label: Corneal arcus
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Individuals with FH may develop corneal arcus (white, gray, or blue opaque ring in the corneal margin as a result of cholesterol deposition) at a younger age than those without FH."
    explanation: Establishes both the sign and the premature timing that gives it diagnostic value.
- category: Cardiovascular
  name: Premature Coronary Artery Atherosclerosis
  description: >-
    Atherosclerotic plaque in the coronary arteries and proximal aorta
    developing decades earlier than in the general population, and in childhood
    in biallelic disease.
  phenotype_term:
    preferred_term: Coronary artery atherosclerosis
    term:
      id: HP:0001677
      label: Coronary artery atherosclerosis
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Familial hypercholesterolemia (FH) is characterized by significantly elevated low-density lipoprotein cholesterol (LDL-C) that leads to atherosclerotic plaque deposition in the coronary arteries and proximal aorta at an early age"
    explanation: States both the lesion and its premature timing.
- category: Cardiovascular
  name: Myocardial Infarction
  description: Coronary event resulting from premature atherosclerotic disease.
  phenotype_term:
    preferred_term: Myocardial infarction
    term:
      id: HP:0001658
      label: Myocardial infarction
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "increases the risk of premature cardiovascular events such as angina and myocardial infarction; stroke occurs more rarely"
    explanation: Names myocardial infarction as a principal clinical event.
- category: Cardiovascular
  name: Angina Pectoris
  description: Effort-related ischemic chest pain from coronary atherosclerosis.
  phenotype_term:
    preferred_term: Angina pectoris
    term:
      id: HP:0001681
      label: Angina pectoris
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "increases the risk of premature cardiovascular events such as angina and myocardial infarction"
    explanation: Names angina as a presenting cardiovascular event.
- category: Cardiovascular
  name: Calcific Aortic Valve Disease
  description: >-
    Aortic valve and aortic root calcification, characteristic of severe
    biallelic disease and less reliably prevented by LDL lowering than coronary
    disease is.
  phenotype_term:
    preferred_term: Aortic valve calcification
    term:
      id: HP:0004380
      label: Aortic valve calcification
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Individuals with a more severe phenotype, often as a result of biallelic variants, can present with very significant elevations in LDL-C (>500 mg/dL), early-onset coronary artery disease (CAD; presenting as early as childhood in some), and calcific aortic valve disease."
    explanation: Identifies calcific aortic valve disease as a feature of severe biallelic disease.
biochemical:
- name: Plasma LDL Cholesterol
  biomarker_term:
    preferred_term: LDL cholesterol
    term:
      id: CHEBI:47774
      label: low-density lipoprotein cholesterol
  presence: Increased
  notes: >-
    The primary diagnostic and monitoring analyte. Reference intervals and
    interpretation bands are not restated here; the diagnostic thresholds used
    in FH are carried on the phenotype entries above and in the diagnosis
    section.
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A clinical diagnosis of FH can be established in a proband with characteristic clinical features and significantly elevated LDL-C levels (typically >190 mg/dL in adults and >160 mg/dL in children)."
    explanation: Establishes LDL-C as the diagnostic analyte and gives its thresholds.
- name: Plasma Apolipoprotein B
  biomarker_term:
    preferred_term: Circulating apolipoprotein B concentration
    term:
      id: HP:0031798
      label: Elevated circulating apolipoprotein B concentration
  presence: Increased
  notes: >-
    Each atherogenic particle carries exactly one apoB-100 molecule, so apoB is
    a particle *count* where LDL-C is a cholesterol *mass*. That distinction
    matters in this disease specifically: the defect is in clearance of
    apoB-100-containing particles, so apoB tracks the quantity the receptor
    actually fails to remove. It also discriminates by allele class - null
    variants carry significantly higher apoB than defective variants in the
    SAFEHEART cohort.
  evidence:
  - reference: PMID:28475941
    reference_title: "Mutational analysis and genotype-phenotype relation in familial hypercholesterolemia: The SAFEHEART registry."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients with null variants have a more severe phenotype than patients with defective variants, presenting with significantly higher levels of atherogenic particles (total cholesterol, LDL-cholesterol and apolipoprotein B)."
    explanation: >-
      Names apolipoprotein B among the atherogenic particle measures elevated in
      this disease, and shows it separating null from defective allele classes.
- name: Lipoprotein(a)
  biomarker_term:
    preferred_term: Circulating lipoprotein(a) concentration
    term:
      id: HP:0430148
      label: Abnormal circulating lipoprotein(a) concentration
  presence: Variable
  notes: >-
    Not caused by the LDLR defect but an independent, additive risk modifier
    within it - and an interpretive trap, because Lp(a)-cholesterol is measured
    within the LDL-C fraction and can inflate an apparent FH phenotype.
  evidence:
  - reference: PMID:24632281
    reference_title: "Lipoprotein(a) levels in familial hypercholesterolemia: an important predictor of cardiovascular disease independent of the type of LDL receptor mutation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "On multivariate analysis, Lp(a) was an independent predictor of cardiovascular disease."
    explanation: Establishes Lp(a) as an independent cardiovascular risk predictor within FH.
  - reference: PMID:24632281
    reference_title: "Lipoprotein(a) levels in familial hypercholesterolemia: an important predictor of cardiovascular disease independent of the type of LDL receptor mutation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The risk of CVD is higher in those patients with an Lp(a) level >50 mg/dl and carrying a receptor-negative mutation in the LDLR gene compared with other less severe mutations."
    explanation: >-
      Shows Lp(a) risk interacting with the receptor class - the highest risk
      stratum is receptor-negative genotype plus high Lp(a).
genetic:
- name: LDLR
  gene_term:
    preferred_term: LDLR
    term:
      id: hgnc:6547
      label: LDLR
  association: Pathogenic Mutations
  presence: Positive
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  gene_disease_validity:
  - validity_classification: DEFINITIVE
    classified_by: CLINGEN
    external_id: CGGV:assertion_81788cfe-7520-4821-b80b-3ee0b2018909-2021-02-24T170000.000Z
    evidence:
    - reference: CGGV:assertion_81788cfe-7520-4821-b80b-3ee0b2018909-2021-02-24T170000.000Z
      reference_title: "LDLR / hypercholesterolemia, familial, 1 (Definitive)"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "LDLR | HGNC:6547 | hypercholesterolemia, familial, 1 | MONDO:0007750 | SD | Definitive"
      explanation: >-
        The ClinGen General Gene Curation Expert Panel classifies the
        LDLR-familial hypercholesterolemia 1 relationship (MONDO:0007750, this
        entry's disease term) as Definitive. ClinGen curates the mode of
        inheritance as semidominant, covering both heterozygous and biallelic
        cases.
    - reference: CGGV:assertion_81788cfe-7520-4821-b80b-3ee0b2018909-2021-02-24T170000.000Z
      reference_title: "LDLR / hypercholesterolemia, familial, 1 (Definitive)"
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: "The mechanism of pathogenicity for this gene-disease relationship is loss of function, in which the receptor is not able to effectively bind and/or internalize plasma LDL for degradation"
      explanation: >-
        ClinGen's evidence summary names loss of receptor function (failure to
        bind and/or internalize LDL) as the disease mechanism, matching the
        trigger node's LOSS_OF_FUNCTION context.
  inheritance:
  - name: Autosomal Dominant
    inheritance_term:
      preferred_term: Autosomal dominant inheritance
      term:
        id: HP:0000006
        label: Autosomal dominant inheritance
  notes: >-
    LDLR at 19p13.2 spans >45 kb in 18 exons that map onto the receptor's
    structural modules. More than 2300 unique FH-associated variants have been
    catalogued - missense (the largest group), nonsense, frameshift, canonical
    and non-canonical splice changes, promoter changes, and exon-level
    deletions and duplications, so deletion/duplication analysis is part of an
    adequate genetic workup and not an optional extra. Variant interpretation
    follows the ClinGen FH Variant Curation Expert Panel's LDLR-specific
    modifications of the ACMG/AMP framework rather than the generic rules.

    The five variant entries below are the *functional* classes - which step of
    the receptor itinerary the allele breaks - and correspond one-to-one with
    the class nodes in the pathophysiology graph. They are orthogonal to the
    ACMG/AMP pathogenicity tiers: an allele has both a class and a
    classification, and only the class predicts response to receptor-directed
    therapy.
  variants:
  - name: Class 1 - null (receptor-negative)
    description: >-
      No LDL receptor protein is synthesized. Large deletions removing the
      promoter, nonsense and frameshift changes, and alleles that make normal
      mRNA but no detectable protein. Homozygotes for two such alleles are
      receptor-negative and respond poorly or not at all to receptor-directed
      drugs.
    type: "null"
    clinical_significance: PATHOGENIC
  - name: Class 2 - transport-defective
    description: >-
      The receptor is synthesized but misfolds and is retained in the
      endoplasmic reticulum instead of maturing through the Golgi to the
      surface. Retention may be complete (2a) or partial (2b).
    type: missense
    clinical_significance: PATHOGENIC
  - name: Class 3 - binding-defective
    description: >-
      Receptor reaches the surface but binds apoB-100 poorly. Changes fall in
      the cysteine-rich ligand-binding repeats or in the EGF-precursor homology
      domain that orients them.
    type: missense
    clinical_significance: PATHOGENIC
  - name: Class 4 - internalization-defective
    description: >-
      Receptor is expressed and binds LDL normally but fails to cluster in
      clathrin-coated pits, because the cytoplasmic internalization signal is
      disrupted. The founding allele is the J.D. mutation, a
      tyrosine-to-cysteine substitution at residue 807.
    type: missense
    clinical_significance: PATHOGENIC
    evidence:
    - reference: PMID:189940
      reference_title: "Analysis of a mutant strain of human fibroblasts with a defect in the internalization of receptor-bound low density lipoprotein."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "In this unique mutant strain (derived from subject J.D.), the cell surface receptor for plasma low density lipoprotein (LDL) was able to bind 125I-labeled LDL normally, but internalization of the receptor-bound lipoprotein failed to occur."
      explanation: >-
        The founding description of this class, in the strain it is named for:
        it establishes a profound internalization defect against preserved
        binding. It supports neither of the two more specific claims in the
        description above - the Y807C substitution and the failure to cluster
        in coated pits were both shown later, and both rest on PMID:3955657,
        cited on the corresponding pathophysiology node.
  - name: Class 5 - recycling-defective
    description: >-
      Receptor binds and internalizes LDL but fails to release it in the
      acidified endosome, so receptor and ligand are degraded together and the
      receptor is not returned to the surface.
    type: missense
    clinical_significance: PATHOGENIC
  evidence:
  - reference: PMID:34906454
    reference_title: "The Clinical Genome Resource (ClinGen) Familial Hypercholesterolemia Variant Curation Expert Panel consensus guidelines for LDLR variant classification."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In this study, we provide consensus recommendations for the most common FH-associated gene, LDLR, where >2300 unique FH-associated variants have been identified."
    explanation: Establishes both LDLR primacy and the scale of the allelic series.
  - reference: PMID:34906454
    reference_title: "The Clinical Genome Resource (ClinGen) Familial Hypercholesterolemia Variant Curation Expert Panel consensus guidelines for LDLR variant classification."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The consensus LDLR variant modifications to existing ACMG/AMP guidelines include (1) alteration of population frequency thresholds, (2) delineation of loss-of-function variant types, (3) functional study criteria specifications, (4) cosegregation criteria specifications, and (5) specific use and thresholds for in silico prediction tools, among others."
    explanation: Names the gene-specific interpretation rules that govern LDLR variant classification.
  - reference: PMID:30306860
    reference_title: "New Horizons in the Pathogenesis, Pathophysiology and Treatment of Familial Hypercholesterolaemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The most common (60-80%) FH cause is mutations of the LDL Receptor (LDLR) protein (6 classes with a different number of receptors and functionality)."
    explanation: >-
      Quantifies the LDLR share of FH and names the receptor-class scheme. Note
      the source counts six classes; the five curated above are the classical
      set, with the sixth (defective basolateral targeting) omitted because no
      quotable functional evidence for it was found.
  - reference: PMID:28475941
    reference_title: "Mutational analysis and genotype-phenotype relation in familial hypercholesterolemia: The SAFEHEART registry."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients with null variants have a more severe phenotype than patients with defective variants, presenting with significantly higher levels of atherogenic particles (total cholesterol, LDL-cholesterol and apolipoprotein B)."
    explanation: >-
      The genotype-phenotype relation that makes the class distinction
      clinically meaningful, in a 2938-patient molecularly diagnosed registry.
  - reference: PMID:30306860
    reference_title: "New Horizons in the Pathogenesis, Pathophysiology and Treatment of Familial Hypercholesterolaemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Recent studies demonstrated the influence of the LDLR mutation type in the FH phenotype, associating a more severe clinical phenotype and worse advanced CVD in patients with null mutation than those with receptor-defective mutations."
    explanation: Independent statement of the null-versus-defective severity gradient.
environmental:
- name: High Saturated and Trans Fat Intake
  description: >-
    Dietary saturated and trans fat add to circulating LDL on top of the
    receptor-mediated clearance defect, so this exposure acts on the lipid
    node rather than only on the vascular outcome. The effect is small in
    absolute terms - trial evidence puts reduced saturated fat intake at a
    small reduction in LDL cholesterol - which is exactly why diet is
    additive to, and never a substitute for, lipid-lowering pharmacotherapy
    here: the inherited component of the LDL burden is present from birth,
    is not diet-derived, and is far larger than diet can move.
  exposure_term:
    preferred_term: high dietary saturated and trans fat exposure
    modifier: INCREASED
    term:
      id: ECTO:0090010
      label: exposure to lipid in food
  influences_mechanisms:
  - target: Lifelong Elevation of Plasma LDL Cholesterol
    environmental_effect: EXACERBATES
    causal_link_type: DIRECT
    description: >-
      Dietary fat intake adds to the circulating LDL burden already produced by
      the inherited receptor deficit, acting on the same plasma LDL quantity.
    evidence:
    - reference: PMID:32827219
      reference_title: "Reduction in saturated fat intake for cardiovascular disease."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "small reductions in weight, serum total cholesterol, LDL cholesterol and BMI"
      explanation: >-
        Cochrane review of randomised trials of reduced saturated fat intake,
        which is the source that actually measures this exposure against the
        node it is attached to. Note the magnitude it reports: small. The
        trials are in general populations, not FH cohorts.
    - reference: PMID:32827219
      reference_title: "Reduction in saturated fat intake for cardiovascular disease."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "greater reductions in saturated fat (reflected in greater reductions in serum cholesterol) resulted in greater reductions in risk of CVD events, explaining most heterogeneity between trials."
      explanation: >-
        The dose-response that carries the exposure through this node to the
        arterial outcome, and the reason the edge is drawn to the lipid node
        rather than straight to the vascular one.
    - reference: PMID:24404629
      reference_title: "Familial Hypercholesterolemia."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "Agents/circumstances to avoid: Smoking, high intake of saturated and trans unsaturated fat, sedentary lifestyle, obesity, hypertension, and diabetes mellitus."
      explanation: >-
        GeneReviews names high saturated and trans fat intake among the
        exposures to avoid in FH; it is grouped here with the exposures acting
        at the lipid level rather than on the arterial wall.
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Prevention of primary manifestations: Heart-healthy diet (including reduced intake of saturated fat and increased intake of soluble fiber to 10-20 g/day); increased physical activity; no smoking."
    explanation: >-
      The corresponding dietary recommendation, which establishes reduced
      saturated fat intake as a modifiable exposure in FH management.
  - reference: PMID:35294538
    reference_title: "Association of the Interaction Between Familial Hypercholesterolemia Variants and Adherence to a Healthy Lifestyle With Risk of Coronary Artery Disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Among carriers, a favorable lifestyle conferred 86% lower risk of CAD compared with an unfavorable lifestyle (hazard ratio, 0.14 [95% CI, 0.04-0.41])."
    explanation: >-
      Quantifies how much the modifiable exposures move the arterial outcome in
      people who already carry an FH variant. The 4-point lifestyle score
      bundles diet, exercise, smoking and obesity, so it does not isolate this
      single exposure, and carriers are pooled across LDLR, APOB and PCSK9
      rather than reported for LDLR alone.
  - reference: PMID:35294538
    reference_title: "Association of the Interaction Between Familial Hypercholesterolemia Variants and Adherence to a Healthy Lifestyle With Risk of Coronary Artery Disease."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "Healthy lifestyle score was only minimally associated with LDL cholesterol concentrations."
    explanation: >-
      Recorded because it qualifies the item above rather than reinforcing it.
      In this cohort the lifestyle score cut coronary risk by 86% while barely
      moving LDL cholesterol, so most of that benefit did not run through the
      plasma LDL node this exposure is wired to. It is cited here as a limit on
      how much of the diet effect the lipid node carries, not as support for
      the edge, which rests on the Cochrane trials above.
  notes: >-
    GeneReviews covers FH across LDLR, APOB and PCSK9, so its statement is
    class-level rather than an LDLR-genotype-specific finding, and the UK
    Biobank lifestyle analysis pools carriers across the same three genes.
- name: Tobacco Smoking
  description: >-
    Smoking's contribution in FH runs predominantly through the arterial wall
    rather than through plasma LDL, which is why it is attached to the
    endothelial node and not to a lipid one. Set against an LDL burden that
    begins at birth and accumulates for decades before the first event,
    cessation matters in absolute terms: carriers move between roughly 35% and
    66% estimated coronary risk by age 75 across lifestyle categories. That is
    an absolute-risk argument, not a claim that carriers benefit more per unit
    of exposure than anyone else - the study reporting those figures found no
    significant interaction between carrier status and lifestyle.
  exposure_term:
    preferred_term: exposure to tobacco smoking
    term:
      id: ECTO:6000029
      label: exposure to tobacco smoking
  influences_mechanisms:
  - target: Endothelial Dysfunction and Subendothelial LDL Retention
    environmental_effect: EXACERBATES
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Smoking aggravates endothelial dysfunction, the permissive condition for
      subendothelial retention of the apoB-containing particles that the
      receptor defect leaves in circulation.
    evidence:
    - reference: PMID:24404629
      reference_title: "Familial Hypercholesterolemia."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "Agents/circumstances to avoid: Smoking, high intake of saturated and trans unsaturated fat, sedentary lifestyle, obesity, hypertension, and diabetes mellitus."
      explanation: >-
        GeneReviews lists smoking first among exposures to avoid in FH. The
        node it is attached to reflects that smoking acts on the arterial wall
        rather than on plasma LDL.
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "reduce CAD risk factors including cessation of smoking, regular physical activity, healthy diet, and weight control"
    explanation: >-
      Smoking cessation is named as part of the coronary risk-factor reduction
      that runs alongside lipid lowering in FH management.
  - reference: PMID:35294538
    reference_title: "Association of the Interaction Between Familial Hypercholesterolemia Variants and Adherence to a Healthy Lifestyle With Risk of Coronary Artery Disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Among carriers, a favorable lifestyle conferred 86% lower risk of CAD compared with an unfavorable lifestyle (hazard ratio, 0.14 [95% CI, 0.04-0.41])."
    explanation: >-
      The size of the lifestyle effect on coronary risk among FH-variant
      carriers. The 4-point score bundles diet, exercise, smoking and obesity,
      so it does not isolate smoking, and carriers are pooled across LDLR, APOB
      and PCSK9.
  - reference: PMID:35294538
    reference_title: "Association of the Interaction Between Familial Hypercholesterolemia Variants and Adherence to a Healthy Lifestyle With Risk of Coronary Artery Disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Similar to the general population, individuals who carry familial hypercholesterolemia variants are likely to benefit from lifestyle interventions to reduce their risk of CAD."
    explanation: >-
      Recorded to bound the previous item. The same analysis found no
      significant interaction between carrier status and lifestyle, so the
      benefit of cessation in carriers is a matter of their higher absolute
      risk rather than of a steeper response to the exposure.
  notes: >-
    GeneReviews covers FH across LDLR, APOB and PCSK9, so its statement is
    class-level rather than an LDLR-genotype-specific finding, and the UK
    Biobank lifestyle analysis pools carriers across the same three genes.
treatments:
- name: Statin (HMG-CoA Reductase Inhibitor) Therapy
  description: >
    First-line, lifelong LDL-lowering therapy. The mechanism is receptor-side
    and therefore genotype-sensitive: inhibiting HMG-CoA reductase lowers
    intracellular cholesterol, which de-represses LDLR transcription and puts
    more receptor on the hepatocyte surface. The drug therefore amplifies
    whatever receptor capacity the genotype leaves. Note that statins have not
    been tested against a receptor-negative genotype stratum in this entry's
    evidence, and the cited mechanistic review reports statins helping both
    homozygous and heterozygous patients, so the null-genotype ceiling is
    inferred from mechanism rather than demonstrated. In a 2146-patient FH cohort followed a
    mean 8.5 years, statin treatment reduced coronary heart disease risk by
    76%.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: statin
      term:
        id: CHEBI:87631
        label: statin
  target_mechanisms:
  - target: Residual Receptor Activity Gates Receptor-Dependent LDL Lowering
    treatment_effect: ACTIVATES
    description: >
      Statins act by inducing residual LDL receptor, so their effect is bounded
      by how much functional receptor the genotype permits.
    evidence:
    - reference: PMID:37371118
      reference_title: "A Review of Progress on Targeting LDL Receptor-Dependent and -Independent Pathways for the Treatment of Hypercholesterolemia, a Major Risk Factor of ASCVD."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "Statins proved to be the first blockbuster drug, helping both HoFH and HeFH individuals by inhibiting the cholesterol synthesis pathway rate-limiting enzyme HMG-CoA reductase and inducing the LDL receptor."
      explanation: States the receptor-inducing mechanism that makes the effect genotype-dependent.
  evidence:
  - reference: PMID:19001495
    reference_title: "Efficacy of statins in familial hypercholesterolaemia: a long term cohort study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We observed an overall risk reduction of 76% (hazard ratio 0.24 (95% confidence interval 0.18 to 0.30), P<0.001)."
    explanation: Quantifies the cardiovascular benefit of statin therapy in an FH cohort.
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "statins can be used in children starting around age eight years"
    explanation: >-
      GeneReviews sets the paediatric initiation age. The recommendation is
      made for FH as a class rather than for LDLR-related FH specifically.
  - reference: PMID:31618540
    reference_title: "20-Year Follow-up of Statins in Children with Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "initiation of statin therapy during childhood in patients with familial hypercholesterolemia slowed the progression of carotid intima-media thickness and reduced the risk of cardiovascular disease in adulthood"
    explanation: >-
      Twenty-year follow-up of a childhood pravastatin trial, genetically
      confirmed in 98% of the 214 patients, showing that treating from
      childhood changes the adult arterial trajectory rather than only the
      lipid number. This is the outcome claim behind starting statins in
      childhood; the GeneReviews item above states only that it is done.
  - reference: PMID:31618540
    reference_title: "20-Year Follow-up of Statins in Children with Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The cumulative incidence of cardiovascular events and of death from cardiovascular causes at 39 years of age was lower among the patients with familial hypercholesterolemia than among their affected parents (1% vs. 26% and 0% vs. 7%, respectively)."
    explanation: >-
      Quantifies that difference against the closest available comparator, the
      patients' own affected parents. Note the residual burden the same study
      reports: mean LDL-C fell only 32%, to 160.7 mg/dL, and just 20% reached
      the treatment goal, so this is the outcome of imperfect lifelong therapy
      rather than of corrected receptor function.
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Statins are contraindicated in pregnancy because of concerns for teratogenicity and should be discontinued prior to conception."
    explanation: >-
      GeneReviews states the pregnancy contraindication. It constrains rather
      than supports the therapy, and is stated at class level.
  notes: >
    Two management constraints carried from the GeneReviews FH chapter, both
    class-level: statins may be started in children from around age eight, and
    they are contraindicated in pregnancy and must be stopped before
    conception - a hard interruption in an otherwise lifelong therapy for a
    disorder transmitted to half of offspring.
- name: PCSK9 Monoclonal Antibody Therapy
  description: >
    Alirocumab and evolocumab neutralize circulating PCSK9, preventing
    PCSK9-directed lysosomal degradation of the LDL receptor and so increasing
    receptor recycling and surface abundance. Like statins this is a
    receptor-amplifying mechanism, and the AMG 145 (evolocumab) homozygous-FH
    study is the cleanest published demonstration that the amplification
    requires a receptor to amplify: LDL cholesterol fell in receptor-defective
    patients and not at all in the receptor-negative ones, within the same
    protocol and at the same doses.
  therapeutic_modality: MONOCLONAL_ANTIBODY
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: PCSK9 inhibitor
      term:
        id: NCIT:C190797
        label: PCSK9 Inhibitor
  target_mechanisms:
  - target: Residual Receptor Activity Gates Receptor-Dependent LDL Lowering
    treatment_effect: ACTIVATES
    description: >
      Blocking PCSK9 spares existing LDL receptor from degradation, raising
      surface receptor abundance in patients who retain functional receptor and
      achieving nothing in those who do not.
    evidence:
    - reference: PMID:24014831
      reference_title: "Effect of the proprotein convertase subtilisin/kexin 9 monoclonal antibody, AMG 145, in homozygous familial hypercholesterolemia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "This study demonstrates significant and dose-related LDL cholesterol lowering with a PCSK9 monoclonal antibody in homozygous familial hypercholesterolemia patients with defective LDL receptor activity but no reduction in those who were receptor negative."
      explanation: The genotype-stratified result that defines the boundary of this therapy.
  evidence:
  - reference: PMID:24014831
    reference_title: "Effect of the proprotein convertase subtilisin/kexin 9 monoclonal antibody, AMG 145, in homozygous familial hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Over the treatment periods, mean±SD LDL cholesterol reductions in the 6 LDL receptor-defective patients were 19.3±16% and 26.3±20% with 4- and 2-week dosing, respectively"
    explanation: Quantifies the response in receptor-defective homozygous disease.
  - reference: PMID:37130090
    reference_title: "2023 Update on European Atherosclerosis Society Consensus Statement on Homozygous Familial Hypercholesterolaemia: new treatments and clinical guidance."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Addition of novel, efficacious therapies (i.e. inhibitors of proprotein convertase subtilisin/kexin type 9, followed by evinacumab and/or lomitapide) offers potential to attain LDL-C goal or reduce the need for LA."
    explanation: Places PCSK9 inhibition in the current consensus treatment sequence for severe disease.
- name: Evinacumab (ANGPTL3 Inhibition)
  description: >
    An angiopoietin-like 3 monoclonal antibody that lowers LDL cholesterol by a
    route that does not require the LDL receptor. This is the therapeutic
    complement of everything above: in the phase 3 homozygous-FH trial it
    lowered LDL cholesterol by a similar amount in patients with null-null
    variants and in those with non-null variants, so it is the option that
    remains when the receptor-directed drugs have nothing to act on.
  therapeutic_modality: MONOCLONAL_ANTIBODY
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: evinacumab
      term:
        id: NCIT:C20401
        label: Monoclonal Antibody
  target_mechanisms:
  - target: Lifelong Elevation of Plasma LDL Cholesterol
    treatment_effect: INHIBITS
    description: >
      Lowers plasma LDL cholesterol without acting through the LDL receptor, so
      the effect is preserved regardless of receptor class.
    evidence:
    - reference: PMID:32813947
      reference_title: "Evinacumab for Homozygous Familial Hypercholesterolemia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The LDL cholesterol level was lower in the evinacumab group than in the placebo group in patients with null-null variants (-43.4% vs. +16.2%) and in those with non-null variants (-49.1% vs. -3.8%)."
      explanation: Demonstrates genotype-independent efficacy, the defining property of this agent.
  evidence:
  - reference: PMID:32813947
    reference_title: "Evinacumab for Homozygous Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "At week 24, patients in the evinacumab group had a relative reduction from baseline in the LDL cholesterol level of 47.1%, as compared with an increase of 1.9% in the placebo group"
    explanation: Reports the primary efficacy result of the pivotal randomized trial.
- name: Lomitapide (Microsomal Triglyceride Transfer Protein Inhibition)
  description: >
    An MTP inhibitor that reduces hepatic assembly and secretion of
    apoB-containing lipoproteins. Like evinacumab it acts upstream of the
    receptor rather than through it, so it is expected to be
    genotype-independent - though, unlike the evinacumab trial, the pivotal
    lomitapide study was single-arm, open-label, and not genotype-stratified,
    so its 50% reduction is a whole-cohort figure and not a demonstration of
    effect in receptor-negative disease specifically. Hepatic steatosis, transaminase elevation,
    gastrointestinal intolerance, and fat-soluble vitamin depletion constrain
    its use and require monitoring.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: lomitapide
      term:
        id: CHEBI:72297
        label: lomitapide
  target_mechanisms:
  - target: Lifelong Elevation of Plasma LDL Cholesterol
    treatment_effect: INHIBITS
    description: >
      Reduces the production side of the LDL steady state rather than the
      clearance side, bypassing the receptor defect entirely.
    evidence:
    - reference: PMID:23122768
      reference_title: "Efficacy and safety of a microsomal triglyceride transfer protein inhibitor in patients with homozygous familial hypercholesterolaemia: a single-arm, open-label, phase 3 study."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "LDL cholesterol was reduced by 50% (95% CI -62 to -39) from baseline"
      explanation: Quantifies LDL lowering in homozygous disease, where receptor-directed drugs underperform.
  evidence:
  - reference: PMID:23122768
    reference_title: "Efficacy and safety of a microsomal triglyceride transfer protein inhibitor in patients with homozygous familial hypercholesterolaemia: a single-arm, open-label, phase 3 study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients with homozygous familial hypercholesterolaemia respond inadequately to existing drugs."
    explanation: States the therapeutic gap that LDLR-independent agents were developed to fill.
  - reference: PMID:23122768
    reference_title: "Efficacy and safety of a microsomal triglyceride transfer protein inhibitor in patients with homozygous familial hypercholesterolaemia: a single-arm, open-label, phase 3 study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Four patients had aminotransaminase levels of more than five times the upper limit of normal, which resolved after dose reduction or temporary interruption of lomitapide."
    explanation: Documents the hepatic toxicity signal that constrains dosing.
- name: Lipoprotein Apheresis
  description: >
    Extracorporeal physical removal of apoB-containing lipoproteins from
    plasma. Wholly independent of LDL receptor function and therefore effective
    in receptor-negative disease, but the effect rebounds between sessions and
    the vascular-access, time, and cost burden is substantial. Current
    consensus places it alongside pharmacotherapy as foundational in severe
    biallelic disease.
  therapeutic_modality: DEVICE
  treatment_term:
    preferred_term: Therapeutic Procedure
    term:
      id: NCIT:C49236
      label: Therapeutic Procedure
  target_mechanisms:
  - target: Lifelong Elevation of Plasma LDL Cholesterol
    treatment_effect: INHIBITS
    description: >
      Removes circulating LDL directly, requiring no receptor and no hepatic
      metabolic step.
    evidence:
    - reference: PMID:37130090
      reference_title: "2023 Update on European Atherosclerosis Society Consensus Statement on Homozygous Familial Hypercholesterolaemia: new treatments and clinical guidance."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Combination LDL-C-lowering therapy-both pharmacologic intervention and lipoprotein apheresis (LA)-is foundational."
      explanation: Establishes apheresis as a foundational component of severe-disease management.
  evidence:
  - reference: PMID:37130090
    reference_title: "2023 Update on European Atherosclerosis Society Consensus Statement on Homozygous Familial Hypercholesterolaemia: new treatments and clinical guidance."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Addition of novel, efficacious therapies (i.e. inhibitors of proprotein convertase subtilisin/kexin type 9, followed by evinacumab and/or lomitapide) offers potential to attain LDL-C goal or reduce the need for LA."
    explanation: Positions apheresis relative to the newer pharmacologic options.
- name: Ezetimibe
  description: >
    Cholesterol-absorption inhibitor (NPC1L1) added to statin therapy when the
    LDL-C target is not reached - step two of the standard FH escalation.
    Curated here because its mechanism is receptor-dependent in the same sense
    statins are: blocking jejunal cholesterol uptake depletes hepatocyte
    cholesterol and drives a compensatory increase in LDL receptor, so like a
    statin it amplifies whatever receptor capacity the genotype leaves rather
    than bypassing the receptor. Statin-plus-ezetimibe reaches roughly 65-70%
    LDL-C reduction against 50-60% for a high-intensity statin alone.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: ezetimibe
      term:
        id: CHEBI:49040
        label: ezetimibe
  target_mechanisms:
  - target: Residual Receptor Activity Gates Receptor-Dependent LDL Lowering
    treatment_effect: ACTIVATES
    description: >
      Ezetimibe belongs on the receptor-dependent side of the gating relation,
      not the LDLR-independent side: it lowers LDL-C by inducing residual
      receptor, so its effect is bounded by the receptor capacity the genotype
      permits.
    evidence:
    - reference: PMID:39076699
      reference_title: "Familial Hypercholesterolemia: Pitfalls and Challenges in Diagnosis and Treatment."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "ezetimibe by blocking cholesterol uptake from the jejunum) result in a  compensatory increase in LDL-R and subsequently enhanced LDL-C clearance."
      explanation: >-
        States that ezetimibe lowers LDL-C through a compensatory increase in
        LDL receptor, which is what places it on the receptor-dependent side of
        the gating node alongside statins.
  evidence:
  - reference: PMID:39076699
    reference_title: "Familial Hypercholesterolemia: Pitfalls and Challenges in Diagnosis and Treatment."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "statins (alone or in combination with ezetimibe) demonstrated a significant  reduction of future ASCVD events even in subjects with LDL-R defective forms"
    explanation: >-
      Supports the event-level benefit of statin-plus-ezetimibe specifically in
      receptor-defective disease, the genotype stratum this entry curates.
  notes: >-
    The umbrella entry (Familial_Hypercholesterolemia) describes ezetimibe as
    "independent of LDLR". That is not the characterization adopted here: the
    cited review states that ezetimibe, like a statin, works through a
    compensatory increase in LDL receptor. Ezetimibe's target is independent of
    LDLR, but its LDL-lowering effect is not, which is the distinction this
    entry's gating node is built to make.
- name: Bempedoic Acid
  description: >
    Oral ATP-citrate lyase inhibitor acting upstream of HMG-CoA reductase.
    Because it is a prodrug activated by a liver-specific enzyme absent from
    skeletal muscle, it is the guideline option for statin-intolerant patients
    - a common situation in a disease requiring lifelong high-intensity statin
    therapy. Like statins and ezetimibe it upregulates LDL receptor activity,
    so it sits on the receptor-dependent side of the gating relation. Reported
    LDL-C reduction was 22.3% in a pooled clinical-heterozygous-FH subgroup.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: bempedoic acid
      term:
        id: CHEBI:149601
        label: bempedoic acid
  target_mechanisms:
  - target: Residual Receptor Activity Gates Receptor-Dependent LDL Lowering
    treatment_effect: ACTIVATES
    description: >
      Inhibiting ATP-citrate lyase depletes hepatic cholesterol and upregulates
      LDL receptor activity by the same de-repression route statins use, so the
      effect is bounded by residual receptor capacity.
    evidence:
    - reference: PMID:39076699
      reference_title: "Familial Hypercholesterolemia: Pitfalls and Challenges in Diagnosis and Treatment."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "It acts as an inhibitor of adenosine triphosphate (ATP) citrate lyase, a  hepatic enzyme that works upstream of HMG-CoA reductase with subsequent  upregulation of LDL-R activity, similar to statins"
      explanation: >-
        States the target and, critically for this entry, that the LDL-lowering
        effect runs through upregulation of LDL receptor activity.
  evidence:
  - reference: PMID:36876740
    reference_title: "Bempedoic Acid and Cardiovascular Outcomes in Statin-Intolerant Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Bempedoic acid, an ATP citrate lyase inhibitor, reduces low-density lipoprotein (LDL) cholesterol levels and is associated with a low incidence of muscle-related adverse events"
    explanation: >-
      CLEAR Outcomes provides the outcome evidence justifying bempedoic acid as
      curated therapy rather than an investigational option.
  notes: >-
    CLEAR Outcomes enrolled statin-intolerant patients at high cardiovascular
    risk, not an LDLR-genotyped or FH-only cohort, so the outcome benefit is not
    LDLR-specific evidence.
- name: Inclisiran (PCSK9-Directed siRNA)
  description: >
    Hepatocyte-targeted small interfering RNA that suppresses PCSK9 synthesis,
    given on days 1 and 90 and every six months thereafter. Mechanistically it
    reaches the same endpoint as a PCSK9 antibody - less PCSK9-mediated
    receptor degradation, therefore more receptor on the hepatocyte surface -
    by inhibiting hepatic PCSK9 production rather than neutralizing circulating
    protein, so it is equally receptor-dependent. ORION-9 (NCT03397121) tested
    it in adults with heterozygous FH.
  therapeutic_modality: SIRNA
  oligonucleotide_details:
    oligonucleotide_mechanism: RNAI_KNOCKDOWN
    target_gene:
      preferred_term: PCSK9
      term:
        id: hgnc:20001
        label: PCSK9
    target_transcript: PCSK9 mRNA
    conjugation: GALNAC
    delivery_platform: CONJUGATE
  dosing_interval: once every 6 months
  dosing_interval_days: 182.5
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: inclisiran
      term:
        id: CHEBI:176399
        label: inclisiran
  target_mechanisms:
  - target: Residual Receptor Activity Gates Receptor-Dependent LDL Lowering
    treatment_effect: ACTIVATES
    description: >
      Suppressing hepatic PCSK9 synthesis preserves receptor that would
      otherwise be degraded, so like the PCSK9 antibodies the effect requires a
      receptor that can be made and can function.
    evidence:
    - reference: PMID:39076699
      reference_title: "Familial Hypercholesterolemia: Pitfalls and Challenges in Diagnosis and Treatment."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "In  contrast to anti-PCSK9 mAbs, inclisiran inactivates PCSK9 by inhibition of its  hepatic synthesis"
      explanation: >-
        Distinguishes the siRNA route to PCSK9 inactivation from antibody
        neutralization while placing both on the same receptor-preserving
        mechanism.
  evidence:
  - reference: PMID:39076699
    reference_title: "Familial Hypercholesterolemia: Pitfalls and Challenges in Diagnosis and Treatment."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "inclisiran represents a first-in-class cholesterol-lowering small interfering  ribonucleic acid (siRNA), targeting PCSK9 messenger RNA (mRNA) in hepatocytes."
    explanation: Establishes the modality and molecular target of the agent.
- name: Liver Transplantation
  description: >
    The limiting case of the receptor-dependent/receptor-independent axis:
    rather than amplifying or bypassing the patient's own receptor, orthotopic
    liver transplantation *supplies* a hepatic LDL receptor complement, which
    is why it can correct the biochemical defect in receptor-negative disease
    that no receptor-directed drug can reach. Reserved for homozygous patients
    whose LDL-C cannot be controlled by maximal medical therapy and apheresis,
    and constrained by operative risk and lifelong immunosuppression. Where
    severe cardiovascular involvement has already developed, combined
    heart-liver transplantation may be required, which is the argument for
    early listing rather than late rescue.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: Organ Transplantation
    term:
      id: NCIT:C15289
      label: Organ Transplantation
  target_mechanisms:
  - target: Reduced Functional Hepatic LDL Receptor Activity
    treatment_effect: ACTIVATES
    description: >
      Replacing the liver replaces the tissue that carries the defective
      receptor, restoring hepatic receptor capacity itself rather than
      modulating the residual capacity a mutant genotype leaves. This is the
      only curated intervention that acts on the receptor-activity node
      directly.
    evidence:
    - reference: PMID:39815304
      reference_title: "Liver transplantation for homozygous familial hypercholesterolemia: a retrospective analysis from Chinese experience."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Accordingly, all 6 patients received orthotopic liver transplantations (OLT), with the result that significant postoperative reductions were observed in levels of TC and LDL."
      explanation: >-
        Reports that supplying a donor liver lowers total and LDL cholesterol,
        which is the receptor-supply mechanism this edge asserts.
  evidence:
  - reference: PMID:39815304
    reference_title: "Liver transplantation for homozygous familial hypercholesterolemia: a retrospective analysis from Chinese experience."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In severe cases of HoFH, clinical signs and symptoms cannot be controlled well by non-surgical treatments, liver transplantation (LT) currently represents the viable option."
    explanation: >-
      Places liver transplantation as the option of last resort when medical
      therapy fails, the clinical position curated here.
  - reference: PMID:39815304
    reference_title: "Liver transplantation for homozygous familial hypercholesterolemia: a retrospective analysis from Chinese experience."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "If severe cardiovascular involvement occurs, LT should be performed as soon as possible, otherwise combined heart-liver transplantation may be required."
    explanation: >-
      Supports the timing argument in the description - that the cost of late
      listing is escalation to combined heart-liver transplantation.
  notes: >-
    The cited series is six patients, retrospective and single-region, so it
    supports the direction of the effect and the clinical positioning but not a
    quantitative estimate of benefit or of transplant-free survival.
- name: Cardiovascular Risk Factor Modification
  description: >
    The receptor defect sets a high baseline arterial risk that conventional
    risk factors multiply. Smoking cessation, control of blood pressure and
    glycemia, weight management, physical activity, and reduced saturated and
    trans fat intake do not correct the LDL level but reduce absolute event
    risk.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Dietary Intervention
    term:
      id: NCIT:C15447
      label: Dietary Intervention
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Agents/circumstances to avoid: Smoking, high intake of saturated and trans unsaturated fat, sedentary lifestyle, obesity, hypertension, and diabetes mellitus."
    explanation: >-
      The GeneReviews agents-and-circumstances-to-avoid list, which is what
      this treatment entry operationalizes.
experimental_models:
- name: J.D. fibroblast strain (internalization-defective LDLR alleles)
  experimental_model_type: PRIMARY_CELL_CULTURE
  description: >-
    Cultured skin fibroblasts from subject J.D., one of 22 fibroblast strains
    from patients with the clinical phenotype of homozygous FH screened by
    Brown and Goldstein. This is the system in which the receptor mutation
    classes were defined: the other 21 strains bound labelled LDL either not
    at all (receptor-negative) or poorly (receptor-defective), while J.D.
    bound LDL normally and failed to internalize it, which is the observation
    that established internalization as a separable step and gave the entry
    its Class 4 allele.

    J.D. is a compound heterozygote, not a true homozygote: a maternal exon
    13-15 deletion producing no functional protein, and a paternal Y807C
    allele producing a receptor that reaches the surface and binds LDL. The
    1976 designation is a pre-molecular clinical label. The cellular phenotype
    is nonetheless cleanly internalization-defective, because the only
    receptor these cells display is the Y807C one.
  cell_source: Patient-derived skin fibroblasts (homozygous FH probands)
  culture_system: Two-dimensional monolayer fibroblast culture
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  cell_types:
  - preferred_term: skin fibroblast
    term:
      id: CL:0002620
      label: skin fibroblast
  publication: PMID:189940
  modeled_mechanisms:
  - target: Defective Clustering in Clathrin-Coated Pits
    relationship: RECAPITULATES
    fidelity: HIGH
    model_scale: CELLULAR
    description: >-
      The founding measurement of this node. Binding and internalization are
      assayed separately in the same cells, so the defect is localized to the
      internalization step rather than inferred from a lowered uptake total.
    limitations: >-
      Fibroblasts are not hepatocytes, and hepatic receptor activity is what
      sets plasma LDL; the strain establishes that the step exists and can be
      broken in isolation, not the quantitative hepatic consequence. The 1976
      report also predates identification of the underlying LDLR sequence
      changes, so what it measures is the cellular phenotype and not the
      alleles, and the compound-heterozygous genotype means the strain reports
      the Y807C allele in the absence of a second functional receptor rather
      than a Class 4 allele in isolation.
    readouts:
    - name: Internalization of receptor-bound 125I-LDL
      target: Defective Clustering in Clathrin-Coated Pits
      direction: DECREASED
      interpretation: >-
        Normal high-affinity binding alongside a profound internalization
        defect in the same cells is the direct measurement this node asserts.
        The 1976 assay recorded no detectable internalization; DECREASED rather
        than ABOLISHED is used because the expression-cloning work this entry
        also cites (PMID:3955657) later showed the Y807C receptor enters the
        cell slowly rather than not at all.
      evidence:
      - reference: PMID:189940
        reference_title: "Analysis of a mutant strain of human fibroblasts with a defect in the internalization of receptor-bound low density lipoprotein."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "the cell surface receptor for plasma low density lipoprotein (LDL) was able to bind 125I-labeled LDL normally, but internalization of the receptor-bound lipoprotein failed to occur"
        explanation: Reports the paired binding and internalization measurements grounding this readout.
    evidence:
    - reference: PMID:189940
      reference_title: "Analysis of a mutant strain of human fibroblasts with a defect in the internalization of receptor-bound low density lipoprotein."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "the defect in this strain differed from the defects found in the fibroblasts from the other 21 FH homozygote strains in which the binding of 125I-LDL to the receptor was either absent (receptor-negative) or markedly reduced (receptor-defective)"
      explanation: >-
        Establishes the contrast against the receptor-negative and
        receptor-defective strains, which is what makes this strain informative
        for internalization specifically rather than for receptor loss in
        general.
- name: JD iPSC-derived hepatocyte-like cells
  experimental_model_type: IPSC_DERIVED_MODEL
  description: >-
    Induced pluripotent stem cells reprogrammed from the same FH patient (JD)
    whose fibroblasts defined the internalization-defective class,
    differentiated into hepatocyte-like cells. Moving the identical genotype
    from fibroblast to hepatocyte is what makes this model informative for the
    plasma-clearance arm: it reads out the receptor defect in the cell type
    that actually clears circulating LDL, and it reproduces the drug-response
    behaviour as well as the uptake defect.
  cell_source: Patient-derived (JD fibroblasts reprogrammed to iPSC)
  culture_system: Two-dimensional hepatocyte-like cell differentiation
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  cell_types:
  - preferred_term: hepatocyte-like cell
    term:
      id: CL:0000182
      label: hepatocyte
  publication: PMID:22653811
  findings:
  - statement: >-
      The same model reports a second, non-clearance abnormality: FH
      hepatocyte-like cells oversecrete lipidated apolipoprotein B-100 roughly
      eight-fold over controls. This entry models the receptor defect as
      impaired clearance only, and that is a deliberate scope limit rather than
      a claim that clearance is the whole mechanism - the authors argue
      explicitly that hepatic apoB-lipoprotein overproduction contributes too.
      No pathophysiology node is asserted for it here because the human
      evidence for an LDLR-specific overproduction arm was not assessed in this
      curation round.
    supporting_text: >-
      FH iPSC-derived hepatocytes display a marked elevation in secretion of
      lipidated apolipoprotein B-100
    evidence:
    - reference: PMID:22653811
      reference_title: "JD induced pluripotent stem cell-derived hepatocytes faithfully recapitulate the pathophysiology of familial hypercholesterolemia."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "FH iPSC-derived hepatocytes display a marked elevation in secretion of lipidated apolipoprotein B-100"
      explanation: >-
        Reports the oversecretion result. Recorded as a finding rather than as
        a mechanism node so that the gap between this model's output and the
        entry's clearance-only pathograph is visible rather than silent.
  modeled_mechanisms:
  - target: Impaired Receptor-Mediated Clearance of Plasma LDL
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: CELLULAR
    description: >-
      Patient-genotype hepatocyte-like cells are deficient in LDL-C uptake
      relative to controls, the cellular counterpart of the plasma clearance
      defect this node asserts.
    limitations: >-
      The node is an organism-level clearance claim and the measurement is
      cellular uptake in culture, so the step from one to the other is
      inferential. iPSC-derived hepatocyte-like cells are also immature
      relative to adult hepatocytes, and the comparison is between individuals
      rather than between isogenic corrected and uncorrected lines, so donor
      background is not controlled.
    readouts:
    - name: LDL-cholesterol uptake by hepatocyte-like cells
      target: Impaired Receptor-Mediated Clearance of Plasma LDL
      direction: DECREASED
      interpretation: >-
        Direct cellular measurement of the receptor-mediated uptake step that
        plasma clearance depends on.
      evidence:
      - reference: PMID:22653811
        reference_title: "JD induced pluripotent stem cell-derived hepatocytes faithfully recapitulate the pathophysiology of familial hypercholesterolemia."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "in contrast to control cells, FH iPSC-derived hepatocytes are deficient in LDL-C uptake"
        explanation: Reports the uptake deficit grounding this readout.
    evidence:
    - reference: PMID:22653811
      reference_title: "JD induced pluripotent stem cell-derived hepatocytes faithfully recapitulate the pathophysiology of familial hypercholesterolemia."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "we produced iPSCs from JD a patient with mutations in the low-density lipoprotein receptor (LDLR) gene that result in familial hypercholesterolemia (FH)"
      explanation: >-
        Establishes that the line carries a patient LDLR genotype, which is
        what makes its uptake behaviour informative for this node.
  - target: Residual Receptor Activity Gates Receptor-Dependent LDL Lowering
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: CELLULAR
    description: >-
      Control hepatocyte-like cells raise LDL uptake when given lovastatin and
      the FH cells do not. The block is not in the drug's proximal action: the
      same study reports that FH cells induce LDLR mRNA on lovastatin to a
      similar extent as controls. What the genotype bounds is the usefulness of
      that induction, because the additional receptor it produces is the
      defective receptor. That is the gating relation observed at the level of
      the hepatocyte itself.
    limitations: >-
      One patient genotype and one drug, measured as cellular uptake rather
      than plasma LDL-C, so the model shows the direction of the gating
      relation and not its dose-response across the allelic series. The node
      also covers receptor-independent agents, on which this model is silent.
    readouts:
    - name: LDL uptake response to lovastatin
      target: Residual Receptor Activity Gates Receptor-Dependent LDL Lowering
      direction: UNCHANGED
      interpretation: >-
        Absence of the drug-induced increase that control cells show is the
        cellular counterpart of a blunted receptor-dependent LDL-lowering
        response.
      evidence:
      - reference: PMID:22653811
        reference_title: "JD induced pluripotent stem cell-derived hepatocytes faithfully recapitulate the pathophysiology of familial hypercholesterolemia."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "control but not FH iPSC-derived hepatocytes increase LDL uptake in response to lovastatin"
        explanation: Reports the differential statin response grounding this readout.
      - reference: PMID:22653811
        reference_title: "JD induced pluripotent stem cell-derived hepatocytes faithfully recapitulate the pathophysiology of familial hypercholesterolemia."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "the extent of induction was similar regardless of genotype"
        explanation: >-
          Locates the block. Receptor induction by the statin is intact in the
          FH cells, so the failure of uptake is downstream of induction, in the
          function of the receptor that induction produces.
    evidence:
    - reference: PMID:22653811
      reference_title: "JD induced pluripotent stem cell-derived hepatocytes faithfully recapitulate the pathophysiology of familial hypercholesterolemia."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "these findings demonstrate that FH iPSC-derived hepatocytes recapitulate the complex pathophysiology of FH in culture"
      explanation: >-
        The authors' own summary claim that the model reproduces FH hepatocyte
        behaviour, which is the basis for treating it as informative here.
- name: CHO-ldlA7 heterologous LDLR variant expression assay
  experimental_model_type: CELL_LINE
  description: >-
    Site-directed LDLR mutants expressed in CHO-ldlA7 cells, a Chinese hamster
    ovary line carrying no endogenous LDL receptor, with surface expression,
    LDL binding and LDL uptake read out separately by flow cytometry. This is
    the assay behind the entry's Functional Characterization of LDLR Variants
    diagnostic item, and because it resolves the three steps separately it is
    the assay family from which class assignment is made - the class call
    itself is a separate claim, cited on that diagnostic item (PMID:25386756)
    rather than here. This paper anchors the model because it states the
    system and the readouts most explicitly; the larger ClinGen-linked
    characterization effort (PMID:34906454) is cited elsewhere in the entry.
  cell_source: LDLR-null cell line (CHO-ldlA7) transfected with the allele under test
  culture_system: Two-dimensional monolayer culture with transient LDLR expression
  organism:
    preferred_term: Chinese hamster
    term:
      id: NCBITaxon:10029
      label: Cricetulus griseus
  publication: PMID:34167030
  modeled_mechanisms:
  - target: Reduced Functional Hepatic LDL Receptor Activity
    relationship: MEASURES
    fidelity: MODERATE
    model_scale: CELLULAR
    description: >-
      Quantifies the residual activity a given LDLR allele supports, resolved
      into the three separable steps - surface expression, binding, uptake -
      that distinguish the receptor classes from one another.
    limitations: >-
      A hamster ovary line transiently overexpressing a human receptor is not a
      hepatocyte: expression level, trafficking machinery and lipoprotein milieu
      all differ, so the assay ranks alleles against each other rather than
      predicting an individual's hepatic receptor activity. This study
      characterized 13 variants and used a 60% activity cut-off, which is an
      operational threshold rather than a measured physiological boundary;
      setting 13 against the more than 2300 variants catalogued elsewhere in
      this entry is a comparison drawn here, not one the paper makes.
    readouts:
    - name: Surface expression, LDL binding and LDL uptake by flow cytometry
      target: Reduced Functional Hepatic LDL Receptor Activity
      direction: DECREASED
      interpretation: >-
        Residual activity below the assay threshold in one or more of the three
        steps is what marks an allele as functionally impairing.
      evidence:
      - reference: PMID:34167030
        reference_title: "LDLR variants functional characterization: Contribution to variant classification."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "cell surface expression, binding and uptake of FITC-LDL were assessed by flow cytometry and Western blot"
        explanation: Names the three measurements that constitute this readout.
    evidence:
    - reference: PMID:34167030
      reference_title: "LDLR variants functional characterization: Contribution to variant classification."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Different LDLR mutants were generated by site-directed mutagenesis and expressed in CHO-ldlA7 cells lacking endogenous expression of LDLR."
      explanation: >-
        Describes the null-background heterologous system, which is what lets
        the readout be attributed to the introduced allele.
    - reference: PMID:34167030
      reference_title: "LDLR variants functional characterization: Contribution to variant classification."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "LDLR mutations are the cause of disease in 90% of the cases but functional studies have only been performed for about 15% of all LDLR variants."
      explanation: >-
        Quantifies how little of the allelic series has been functionally
        characterized, which is the gap this class of assay exists to close.
- name: Activity-normalized prime editing saturation screen of LDLR coding variants
  experimental_model_type: CELL_LINE
  description: >-
    Pooled prime-editing screen installing 5,184 LDLR coding variants at the
    endogenous locus in human cells and scoring each for LDL-cholesterol
    uptake, with a genotypic outcome reporter paired to every guide so scores
    can be normalized for editing efficiency. It is the saturation counterpart
    of the one-variant-at-a-time heterologous assay above: instead of ranking a
    handful of alleles it maps the whole coding series onto a continuous
    activity scale, and because the variant sits at the endogenous locus it
    also catches splice-altering coding changes that complementary-DNA
    constructs cannot express.
  cell_source: Human cells carrying prime-edited LDLR at the endogenous locus
  culture_system: Pooled two-dimensional culture with fluorescence-based LDL uptake sorting
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  publication: PMID:42677454
  modeled_mechanisms:
  - target: Reduced Functional Hepatic LDL Receptor Activity
    relationship: MEASURES
    fidelity: MODERATE
    model_scale: CELLULAR
    description: >-
      Measures residual LDL uptake for each of 5,184 coding variants, turning
      the receptor-activity axis this node represents into a per-allele
      quantity that separates known pathogenic from known benign variants and
      tracks LDL-C in an independent human cohort.
    limitations: >-
      Uptake is a single composite readout, so unlike the stepwise flow
      cytometry assay it does not resolve which step of the receptor itinerary
      an allele breaks and therefore does not by itself assign a receptor
      class. It covers coding variants only, leaving promoter changes and
      exon-level deletions untouched, and the functional score is calibrated as
      evidence toward classification rather than as a diagnosis in its own
      right.
    readouts:
    - name: Per-variant LDL-cholesterol uptake score
      target: Reduced Functional Hepatic LDL Receptor Activity
      direction: DECREASED
      interpretation: >-
        A continuous activity score per allele, anchored by the separation of
        pathogenic from benign ClinVar variants and by concordance with
        measured LDL-C in carriers.
      evidence:
      - reference: PMID:42677454
        reference_title: "LDLR Variant Classification Through Activity-Normalized Prime Editing Screening."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "The resulting scores capture a continuous spectrum of functional effects, robustly separate pathogenic versus benign ClinVar variants, and show concordance with LDL-C levels in UK Biobank participants."
        explanation: >-
          Reports both the score itself and the two external anchors that make
          it interpretable as receptor activity.
    evidence:
    - reference: PMID:42677454
      reference_title: "LDLR Variant Classification Through Activity-Normalized Prime Editing Screening."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "We developed the first activity-normalized prime editing screening pipeline to measure the impact of 5184 LDLR coding variants on LDL-cholesterol (LDL-C) uptake."
      explanation: >-
        Describes the assay and its scale, which is what makes it informative
        for the receptor-activity node across the allelic series rather than
        for one allele.
    - reference: PMID:42677454
      reference_title: "LDLR Variant Classification Through Activity-Normalized Prime Editing Screening."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "prime editing uniquely detects splice-altering coding variants missed by cDNA-based screens and pathogenicity predictors, revealing an advantage of endogenous variant installation"
      explanation: >-
        The specific advantage of editing the endogenous locus, and the reason
        this model is not redundant with construct-based assays of the same
        node.
  notes: >-
    The screen also reports a cluster of gain-of-function variants in
    ligand-binding repeat 5, at least some of which raise LDL uptake through
    increased apolipoprotein B interaction. Those alleles are not part of this disease - they are the
    mirror image of it - and are noted here only because they come from the
    same experiment and bear on therapeutic genome editing.
datasets:
- accession: geo:GSE329001
  title: LDLR variant classification through activity-normalized prime editing screening
  description: >-
    Pooled activity-normalized prime-editing screen installing 5,184 LDLR
    coding variants in a human cell line and reading out LDL-cholesterol
    uptake, with each pegRNA paired to a genotypic outcome reporter so
    phenotypic scores can be corrected for editing efficiency. Manually
    relevance-triaged: the series is about the LDLR allelic series itself -
    which coding change breaks which step of receptor function - which is the
    axis this entry is built on, not merely about a gene that FH shares with
    other entries.
  data_type: MULTI_OMICS_PERTURBATION
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  genes:
  - preferred_term: LDLR
    term:
      id: hgnc:6547
      label: LDLR
  publication: PMID:42677454
  evidence:
  - reference: GEO:GSE329001
    reference_title: "LDLR variant classification through activity-normalized prime editing screening"
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "We developed an innovative, activity-normalized prime editing screening pipeline to measure the impact of 5,184 LDLR coding variants on LDL-cholesterol (LDL-C) uptake."
    explanation: >-
      The repository record's own statement of what the series contains, which
      is what makes it the dataset for the allelic-series axis of this entry.
  notes: >-
    Surfaced by `just discover-datasets` as a DIRECT candidate and confirmed
    against the linked publication before inclusion. The evidence item quotes
    the cached GEO record itself; the screen's scientific findings are cited
    from the publication on the corresponding experimental model instead.
- accession: geo:GSE126352
  title: Transcriptomes of human monocytes from patients with familial hypercholesterolemia before and after statin treatment
  description: >-
    RNA sequencing of circulating monocytes from familial hypercholesterolemia
    patients before and after three months of statin therapy, generated to ask
    whether lowering LDL reverses the trained-immunity phenotype of those
    cells. Relevant here to the monocyte arm of the arterial cascade and to
    what statin therapy does and does not undo. Relevance caveat: the cohort is
    defined clinically as familial hypercholesterolemia and the series does not
    report LDLR genotypes, so it is class-level rather than LDLR-specific.
  data_type: BULK_RNA_SEQ
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  publication: PMID:31204280
  evidence:
  - reference: GEO:GSE126352
    reference_title: "Transcriptomes of human monocytes from patients with familial hypercholesterolemia before and after statin treatment"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "in this study we compared the transcriptomes of patients with hypercholesterolemia before and after statin treatment for 3 months"
    explanation: >-
      The repository record's own statement of the design, which is what
      establishes the before/after statin comparison this record is cited for.
  notes: >-
    Surfaced by `just discover-datasets` as a DIRECT candidate and confirmed
    against the linked publication before inclusion.
- accession: geo:GSE178126
  title: Circulating miRNA profile and coronary calcification in asymptomatic patients with familial hypercholesterolemia.
  description: >-
    Microarray profiling of plasma microRNAs in asymptomatic familial
    hypercholesterolemia patients stratified by coronary artery calcium score
    on computed tomographic angiography. Relevant to the subclinical phase of
    the arterial arm - patients who already carry the lifelong LDL burden but
    have not yet had an event. Relevance caveat: the cohort is defined
    clinically and the series does not report LDLR genotypes, so it is
    class-level rather than LDLR-specific.
  data_type: MICROARRAY
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  publication: PMID:38513437
  evidence:
  - reference: GEO:GSE178126
    reference_title: "Circulating miRNA profile and coronary calcification in asymptomatic patients with familial hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We used miRNA arrays to profile miRNAs isolated from plasma from familial hypercholesterolemia patients with (FH-W_CCS) or without (FH-WO_CCS) coronary calcium score by computed tomographic angiography"
    explanation: >-
      The repository record's own statement of the stratification, which is
      what makes this series about the subclinical arterial phase rather than
      about FH generally.
  notes: >-
    Surfaced by `just discover-datasets` as a DIRECT candidate and confirmed
    against the linked publication before inclusion.
animal_models:
- name: Ldlr-knockout mouse
  species: Mouse
  genotype: Ldlr-/- (homologous recombination in embryonic stem cells)
  publication: PMID:8349823
  description: >-
    The founding genetic model. Viable and fertile, with a selective rise in
    IDL and LDL and a demonstrated prolongation of apoB-lipoprotein clearance,
    and reversible by hepatic re-expression of the human receptor - which
    closes the causal loop between receptor absence and hypercholesterolemia.
  modeled_mechanisms:
  - target: Impaired Receptor-Mediated Clearance of Plasma LDL
    relationship: RECAPITULATES
    fidelity: HIGH
    description: >-
      Directly measures the clearance defect that this node represents, in the
      cleanest possible genetic background - complete receptor absence.
    limitations: >-
      Murine lipoprotein metabolism is apoB48- and HDL-dominated rather than
      LDL-dominated, so absolute cholesterol levels are far below human
      homozygous FH and spontaneous atherosclerosis on chow is limited; the
      model reproduces the clearance defect faithfully but not the human
      lipoprotein distribution or the arterial disease burden.
    readouts:
    - name: Plasma clearance half-life of radiolabelled VLDL and LDL
      target: Impaired Receptor-Mediated Clearance of Plasma LDL
      direction: INCREASED
      interpretation: >-
        Prolonged half-life is the direct measurement of the clearance defect;
        normal HDL clearance in the same animals shows the defect is
        ligand-specific.
      evidence:
      - reference: PMID:8349823
        reference_title: "Hypercholesterolemia in low density lipoprotein receptor knockout mice and its reversal by adenovirus-mediated gene delivery."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "The half-lives for intravenously administered 125I-VLDL and 125I-LDL were prolonged by 30-fold and 2.5-fold, respectively, but the clearance of 125I-HDL was normal in the LDLR-/- mice."
        explanation: Reports the measured clearance half-lives underlying this readout.
    evidence:
    - reference: PMID:8183926
      reference_title: "The two-receptor model of lipoprotein clearance: tests of the hypothesis in \"knockout\" mice lacking the low density lipoprotein receptor, apolipoprotein E, or both proteins."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "LDLR(-/-) mice had a relatively isolated elevation in plasma LDL"
      explanation: >-
        Confirms that the model isolates the LDL clearance arm rather than
        producing a generalized dyslipidemia.
  - target: Reduced Functional Hepatic LDL Receptor Activity
    relationship: RESCUES
    fidelity: HIGH
    description: >-
      Restoring hepatic LDL receptor expression by adenoviral delivery
      normalized the elevated IDL/LDL within four days, demonstrating that the
      receptor deficit is both necessary and sufficient for the phenotype in
      this model.
    limitations: >-
      Adenoviral rescue is acute and supraphysiological hepatic overexpression,
      not a model of the endogenous allelic series; it establishes sufficiency
      of receptor restoration, not the dose-response of partial residual
      activity.
    readouts:
    - name: Plasma IDL/LDL cholesterol after hepatic LDLR re-expression
      target: Reduced Functional Hepatic LDL Receptor Activity
      direction: RESTORED
      interpretation: >-
        Normalization on receptor restoration is the rescue arm of the causal
        claim.
      evidence:
      - reference: PMID:8349823
        reference_title: "Hypercholesterolemia in low density lipoprotein receptor knockout mice and its reversal by adenovirus-mediated gene delivery."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "The elevated IDL/LDL level of LDLR-/- mice was reduced to normal 4 d after the intravenous injection of a recombinant replication-defective adenovirus encoding the human LDL receptor driven by the cytomegalovirus promoter."
        explanation: Reports the rescue measurement.
    evidence:
    - reference: PMID:8349823
      reference_title: "Hypercholesterolemia in low density lipoprotein receptor knockout mice and its reversal by adenovirus-mediated gene delivery."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "The virus restored expression of LDL receptor protein in the liver and increased the clearance of 125I-VLDL."
      explanation: Confirms that the rescue acted through restored hepatic receptor protein.
- name: Watanabe heritable hyperlipidemic (WHHL) rabbit
  species: Rabbit
  genotype: Naturally occurring homozygous LDL receptor deficiency
  publication: PMID:31748469
  description: >-
    A spontaneously arising LDL-receptor-deficient rabbit strain and its
    coronary-atherosclerosis-prone and myocardial-infarction-prone derivatives.
    Rabbit lipoprotein metabolism is far closer to human than murine, and this
    is the model in which the LDL receptor pathway hypothesis - derived from
    cultured fibroblasts - was shown to hold in a whole animal, and in which
    the arterial consequences of lifelong receptor deficiency were worked out.
  modeled_mechanisms:
  - target: Endothelial Dysfunction and Subendothelial LDL Retention
    relationship: RECAPITULATES
    fidelity: HIGH
    description: >-
      Spontaneous, diet-independent hypercholesterolemia from receptor
      deficiency drives the initiating arterial events - oxidized LDL
      accumulation, endothelial adhesion molecule expression, and monocyte
      infiltration.
    limitations: >-
      Rabbits lack the human coronary anatomy and plaque-rupture triggers in
      full, and the reviewed strain history reports that lesion rupture in this
      model requires secondary mechanical forces such as spasm, so event
      generation is not a faithful analogue of human acute coronary syndrome.
    readouts:
    - name: Arterial intimal macrophage infiltration and oxidized LDL accumulation
      target: Endothelial Dysfunction and Subendothelial LDL Retention
      direction: INCREASED
      interpretation: >-
        Histological demonstration of the initiating steps of atherogenesis in
        a receptor-deficient animal.
      evidence:
      - reference: PMID:31748469
        reference_title: "The History of the WHHL Rabbit, an Animal Model of Familial Hypercholesterolemia (I) - Contribution to the Elucidation of the Pathophysiology of Human Hypercholesterolemia and Coronary Heart Disease."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Oxidized LDL accumulates in the arterial wall, monocyte adhesion molecules are expressed on arterial endothelial cells, and monocyte-derived macrophages infiltrate the arterial intima, resulting in the formation and progression of atherosclerosis."
        explanation: Reports the arterial findings underlying this readout.
    evidence:
    - reference: PMID:31748469
      reference_title: "The History of the WHHL Rabbit, an Animal Model of Familial Hypercholesterolemia (I) - Contribution to the Elucidation of the Pathophysiology of Human Hypercholesterolemia and Coronary Heart Disease."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "The main part of human lipoprotein metabolism has been elucidated, and the low-density lipoprotein (LDL) receptor pathway hypothesis derived from studies using fibroblasts was proven in vivo."
      explanation: >-
        Establishes this strain as the in vivo proof of the receptor pathway,
        which is why it is informative for the arterial arm.
- name: LDLR-knockout cynomolgus monkey
  species: Cynomolgus monkey
  genotype: LDLR knockout by genome editing (six founder animals)
  publication: PMID:37730951
  description: >-
    A genome-edited non-human primate model. Plasma cholesterol reached levels
    comparable to human homozygous FH, periocular xanthoma appeared within the
    first year, and the animals were strongly resistant to lipid-lowering
    medication - the primate counterpart of the receptor-negative
    pharmacological phenotype.
  modeled_mechanisms:
  - target: Residual Receptor Activity Gates Receptor-Dependent LDL Lowering
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Complete receptor knockout reproduces the drug-refractory phenotype that
      defines receptor-negative homozygous disease.
    limitations: >-
      Six founder animals, possible mosaicism from editing, short follow-up,
      and the report characterizes drug resistance in aggregate rather than
      drug-by-drug, so it supports the direction of the gating relation but not
      an agent-specific magnitude.
    readouts:
    - name: LDL cholesterol response to lipid-lowering medication
      target: Residual Receptor Activity Gates Receptor-Dependent LDL Lowering
      direction: UNCHANGED
      interpretation: >-
        Failure to respond in a total-knockout primate is the model-side
        counterpart of the absent response in receptor-negative patients.
      evidence:
      - reference: PMID:37730951
        reference_title: "Generation of a familial hypercholesterolemia model in non-human primate."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "The LDLR KO monkeys were also strongly resistant to medications for hypercholesterolemia."
        explanation: Reports the drug-resistance observation underlying this readout.
    evidence:
    - reference: PMID:37730951
      reference_title: "Generation of a familial hypercholesterolemia model in non-human primate."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "The levels of plasma cholesterol and triglyceride were quite high in the monkeys, and were similar to those in FH patients with homozygous mutations in the LDLR gene."
      explanation: >-
        Establishes that the model reaches human homozygous-FH lipid levels,
        which is what makes its drug-response behaviour informative.
clinical_trials:
- name: NCT03399786
  phase: PHASE_III
  status: COMPLETED
  description: >-
    ELIPSE HoFH. Randomized, double-blind, placebo-controlled trial of
    intravenous evinacumab in 65 patients with homozygous familial
    hypercholesterolemia, reporting results separately for null-null and
    non-null LDL-receptor genotypes - the trial that established
    LDLR-independent LDL lowering in receptor-negative disease.
  target_phenotypes:
  - preferred_term: Increased LDL cholesterol concentration
    term:
      id: HP:0003141
      label: Increased LDL cholesterol concentration
  evidence:
  - reference: clinicaltrials:NCT03399786
    reference_title: "A Randomized, Double-blind, Placebo-controlled, Parallel-group Study to Evaluate the Efficacy and Safety of Evinacumab in Patients With Homozygous Familial Hypercholesterolemia"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The primary objective of the study is to demonstrate the reduction of low-density lipoprotein cholesterol (LDL-C) by evinacumab intravenously (IV) in comparison to placebo after 24 weeks in patients with homozygous familial hypercholesterolemia (HoFH)."
    explanation: States the trial's primary objective in the population relevant to this entry.
- name: NCT04233918
  phase: PHASE_III
  status: COMPLETED
  description: >-
    Three-part, single-arm, open-label study of evinacumab in paediatric
    patients with homozygous familial hypercholesterolemia, extending the
    LDLR-independent option to children, in whom receptor-negative disease
    presents earliest.
  target_phenotypes:
  - preferred_term: Increased LDL cholesterol concentration
    term:
      id: HP:0003141
      label: Increased LDL cholesterol concentration
  evidence:
  - reference: clinicaltrials:NCT04233918
    reference_title: "A Three-Part, Single-Arm, Open-Label Study to Evaluate the Efficacy, Safety, and Pharmacokinetics of Evinacumab in Pediatric Patients With Homozygous Familial Hypercholesterolemia"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The primary objective for Part B of the study is to demonstrate a reduction of low-density lipoprotein cholesterol (LDL-C) by evinacumab in pediatric (5 to 11 years of age) patients with HoFH."
    explanation: States the trial's efficacy objective in the paediatric homozygous population.
- name: NCT03397121
  phase: PHASE_III
  status: COMPLETED
  description: >-
    ORION-9. Placebo-controlled, double-blind, randomized trial of inclisiran,
    a hepatocyte-targeted siRNA that suppresses PCSK9 synthesis, in adults with
    heterozygous familial hypercholesterolemia - a receptor-amplifying
    mechanism tested in the population that retains residual receptor.
  target_phenotypes:
  - preferred_term: Increased LDL cholesterol concentration
    term:
      id: HP:0003141
      label: Increased LDL cholesterol concentration
  evidence:
  - reference: clinicaltrials:NCT03397121
    reference_title: "Placebo-Controlled, Double-Blind, Randomized Trial to Evaluate the Effect of 300 mg of Inclisiran Sodium Given as Subcutaneous Injections in Subjects With Heterozygous Familial Hypercholesterolemia (HeFH) and Elevated Low-Density Lipoprotein Cholesterol (LDL-C)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This is a Phase III, placebo-controlled, double-blind, randomized study in participants with HeFH and elevated LDL-C to evaluate the efficacy, safety, and tolerability of subcutaneous (SC) injection(s) of inclisiran."
    explanation: States the trial design, population, and agent.
- name: NCT06597006
  phase: PHASE_III
  status: RECRUITING
  description: >-
    Two-part randomized study of inclisiran in children aged 2 to under 12 with
    homozygous familial hypercholesterolemia. Curated because it is the most
    directly on-thesis trial available for this entry: its enrolment criteria
    operationalize the gating relation itself, requiring documented biallelic
    null LDLR mutations and excluding children with poor prior response to a
    PCSK9 antibody - i.e. it tests a receptor-preserving agent in exactly the
    genotype stratum where receptor-directed therapy is predicted to fail.
  target_phenotypes:
  - preferred_term: Increased LDL cholesterol concentration
    term:
      id: HP:0003141
      label: Increased LDL cholesterol concentration
  evidence:
  - reference: clinicaltrials:NCT06597006
    reference_title: "Two Part (Double-blind Inclisiran Versus Placebo [Year 1] Followed by Open-label Inclisiran [Year 2]) Randomized Multicenter Study to Evaluate Safety, Tolerability, and Efficacy of Inclisiran in Children (2 to Less Than 12 Years) With Homozygous Familial Hypercholesterolemia and Elevated LDL-cholesterol"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'This is a pivotal phase III study designed to evaluate safety, tolerability, and efficacy of inclisiran in children (aged 2 to \<12 years) with homozygous familial hypercholesterolemia (HoFH) and elevated low density lipoprotein cholesterol (LDLC).'
    explanation: >-
      States the design and the homozygous paediatric population; the
      genotype-specific enrolment detail is recorded in the description from the
      registry record rather than quoted, as the cached summary does not carry
      the eligibility text.
diagnosis:
- name: Molecular Genetic Testing of LDLR
  description: >-
    Sequencing of LDLR together with APOB and PCSK9, plus deletion/duplication
    analysis, since exon-level copy-number changes are a real and
    sequencing-invisible part of the LDLR allelic series. Variant
    interpretation should follow the ClinGen FH Variant Curation Expert Panel's
    LDLR-specific specification of the ACMG/AMP framework rather than the
    generic rules, which is what makes a confident pathogenic call - and
    therefore cascade testing of relatives - possible.
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The molecular diagnosis of FH can be established by identification of heterozygous or biallelic pathogenic variants in APOB (variants that impair binding of LDL-C to the LDL receptor), LDLR, or PCSK9 (gain of function); or rarely, identification of biallelic pathogenic variants in LDLRAP1."
    explanation: States the molecular diagnostic route and the genes tested.
  - reference: PMID:34906454
    reference_title: "The Clinical Genome Resource (ClinGen) Familial Hypercholesterolemia Variant Curation Expert Panel consensus guidelines for LDLR variant classification."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Establishment of these guidelines as the new standard in the clinical laboratory setting will result in a more evidence-based, harmonized method for LDLR variant classification worldwide, thereby improving the care of patients with FH."
    explanation: Names the gene-specific interpretation standard that governs the diagnostic call.
- name: Functional Characterization of LDLR Variants
  description: >-
    Cell-based assays - LDL binding and uptake by flow cytometry with
    fluorescent LDL, receptor expression by immunofluorescence or Western blot,
    and receptor localization by confocal microscopy - performed in
    receptor-deficient CHO-ldlA7 cells transfected with the patient allele.
    These assays do two things no in silico predictor can: they resolve
    variants of uncertain significance into a pathogenicity call, and they
    assign the allele to a functional class, which is the input to
    genotype-guided therapy selection.
  evidence:
  - reference: PMID:25386756
    reference_title: "Advantages and versatility of fluorescence-based methodology to characterize the functionality of LDLR and class mutation assignment."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Additionally confocal microscopy allowed the assignment of different class mutation to the variants assayed."
    explanation: Establishes class assignment as an output of the functional assay.
  - reference: PMID:31106925
    reference_title: "Functional analysis of new variants at the low-density lipoprotein receptor associated with familial hypercholesterolemia."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "This approach allows us to confirm the genetic diagnosis of FH, avoiding the classification as \"uncertain significant variants\", and therefore, carry out cascade family screening."
    explanation: States the clinical consequence of functional characterization - VUS resolution enabling cascade screening.
  - reference: PMID:37847331
    reference_title: "Predictive Modeling and Structure Analysis of Genetic Variants in Familial Hypercholesterolemia: Implications for Diagnosis and Protein Interaction Studies."
    supports: SUPPORT
    evidence_source: COMPUTATIONAL
    snippet: "Despite their contributions, a definitive diagnosis of a genetic variant necessitates functional validation through in vitro characterization or cascade screening."
    explanation: >-
      States that computational prediction alone is insufficient, which is why
      the functional assay is curated as its own diagnostic modality.
differential_diagnoses:
- name: Familial defective apolipoprotein B-100 (APOB)
  description: >-
    The ligand-side mirror of this entry. Clinically indistinguishable at the
    bedside and separated only by molecular testing: here the receptor is
    defective, there the receptor is normal and the apoB-100 ligand it must
    recognize is not. Curated separately as
    Familial_Defective_Apolipoprotein_B-100 (MONDO:0007751). LDL-C elevation is
    generally milder than in LDLR-related disease.
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The molecular diagnosis of FH can be established by identification of heterozygous or biallelic pathogenic variants in APOB (variants that impair binding of LDL-C to the LDL receptor), LDLR, or PCSK9 (gain of function); or rarely, identification of biallelic pathogenic variants in LDLRAP1."
    explanation: >-
      GeneReviews names APOB as an alternative molecular cause of the same
      clinical picture and specifies its distinguishing mechanism - impaired
      binding of LDL-C to the receptor rather than a defective receptor.
- name: Autosomal dominant hypercholesterolemia 3 (PCSK9 gain of function)
  description: >-
    The regulator-side member of the dominant trio. The receptor gene is
    intact; a gain-of-function PCSK9 variant degrades normal receptor
    prematurely, so receptor number falls without any receptor defect. Curated
    separately as Autosomal_Dominant_Hypercholesterolemia_3 (MONDO:0011369).
    The practical consequence is therapeutic: PCSK9-directed agents address the
    causal lesion there, whereas here they amplify a residual receptor.
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The molecular diagnosis of FH can be established by identification of heterozygous or biallelic pathogenic variants in APOB (variants that impair binding of LDL-C to the LDL receptor), LDLR, or PCSK9 (gain of function); or rarely, identification of biallelic pathogenic variants in LDLRAP1."
    explanation: >-
      GeneReviews lists PCSK9 gain of function as a distinct molecular route to
      the same phenotype.
- name: Autosomal recessive hypercholesterolemia (LDLRAP1)
  description: >-
    The phenocopy of this entry acting in trans. LDLRAP1 encodes the adaptor
    that couples the receptor to the clathrin endocytic machinery, so biallelic
    loss produces functionally the same internalization failure as a class 4
    LDLR allele while the receptor itself is normal. Recessive rather than
    dominant, so parents are typically unaffected - the pedigree pattern is
    usually what separates it clinically.
  evidence:
  - reference: PMID:24404629
    reference_title: "Familial Hypercholesterolemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "or rarely, identification of biallelic pathogenic variants in LDLRAP1."
    explanation: >-
      GeneReviews records LDLRAP1 as the rare biallelic route to a clinical FH
      diagnosis, distinguishing it from the dominant genes by inheritance.
- name: Polygenic hypercholesterolemia
  description: >-
    The most common alternative explanation for a clinical FH phenotype with no
    identified monogenic variant: the cumulative effect of many small LDL-C
    raising alleles can reach the same LDL-C range as a monogenic defect.
    Distinguishing it matters because cardiovascular risk, cascade-testing
    yield, and treatment responsiveness differ from monogenic disease, and
    because a negative LDLR test does not exclude clinical FH.
  evidence:
  - reference: PMID:39076699
    reference_title: "Familial Hypercholesterolemia: Pitfalls and Challenges in Diagnosis and Treatment."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "would suggest polygenic causes of FH, where small but cumulative effects of several LDL-C raising alleles can cause the LDL-C increase up to the same range as that"
    explanation: >-
      States that polygenic burden can reproduce the monogenic LDL-C range,
      which is what makes it the principal differential for a variant-negative
      clinical FH phenotype.
- name: Elevated lipoprotein(a) mimicking familial hypercholesterolemia
  description: >-
    Not a separate disease so much as a measurement artefact that produces the
    same referral. Conventional LDL-C assays cannot separate LDL-cholesterol
    from lipoprotein(a)-cholesterol because the particles overlap in density,
    so a high Lp(a) inflates measured LDL-C and can push a patient into a
    clinical FH category they do not belong in. Relevant to this entry because
    Lp(a) is also genuinely elevated in FH and is curated as a biomarker here.
  evidence:
  - reference: PMID:39076699
    reference_title: "Familial Hypercholesterolemia: Pitfalls and Challenges in Diagnosis and Treatment."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Conventional assays for LDL-C determination quantify a composite of atherogenic cholesterol, which is attributable not only to LDL-C, but also to lipoprotein(a)-cholesterol (Lp(a)-C) due to their overlapping densities."
    explanation: >-
      Explains the assay overlap that lets high Lp(a) masquerade as the elevated
      LDL-C used to make a clinical FH diagnosis.
- name: Sitosterolemia, dysbetalipoproteinemia, and cholesteryl ester storage disease
  description: >-
    Distinctive non-FH inherited dyslipidemias that can present with severe
    hypercholesterolemia and xanthoma and so enter the differential of a young
    patient with very high LDL-C and no LDLR variant - sitosterolemia (ABCG5 /
    ABCG8), dysbetalipoproteinemia (APOE), and cholesteryl ester storage
    disease / lysosomal acid lipase deficiency (LIPA). Each has its own
    mechanism and, importantly, its own treatment, so misassignment to FH has
    therapeutic consequences.
  evidence:
  - reference: PMID:39076699
    reference_title: "Familial Hypercholesterolemia: Pitfalls and Challenges in Diagnosis and Treatment."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "some of these genes might also cause distinctive non-FH syndromes such as sitosterolemia (ABCG5), dysbetalipoproteinemia (APOE) or cholesteryl ester storage disease (LIPA)"
    explanation: >-
      Names the non-FH inherited dyslipidemias that share the severe
      hypercholesterolemia presentation.
discussions:
- discussion_id: residual_ldlr_activity_response_threshold
  kind: KNOWLEDGE_GAP
  attaches_to:
  - "pathophysiology#Reduced Functional Hepatic LDL Receptor Activity"
  prompt: >-
    What residual LDL receptor activity threshold actually separates patients
    who will respond to receptor-directed therapy from those who will not; is
    that threshold the same for statins as for PCSK9-directed agents; and do
    statins in fact lose effect in receptor-negative disease at all, given that
    this has never been tested against an untreated null-genotype stratum?
  rationale: >-
    The entry curates residual receptor activity as the quantity that gates
    receptor-dependent LDL lowering, and the direction of that relation is well
    evidenced. The threshold is not. "Null" has been defined at under 2% of
    wild-type activity in functional-assay literature and operationalized as
    high as 15% in trial protocols, and the pivotal genotype-stratified
    observation rests on two receptor-negative patients. Nor is it established
    that statins (which act transcriptionally, on synthesis) and PCSK9-directed
    agents (which act post-translationally, on degradation and recycling) share
    a threshold - a class 1 null allele leaves nothing for either to act on,
    but a class 5 recycling-defective allele might respond differently to the
    two mechanisms. The asymmetry is sharper than that: the only
    genotype-stratified test in this entry is of a PCSK9 antibody, and its two
    receptor-negative patients were already on stable statin therapy at
    enrolment, so statins have never been shown here to fail in
    receptor-negative disease - and the entry's own cited mechanistic review
    reports statins helping both homozygous and heterozygous patients. The
    null-genotype ceiling for statins is therefore inferred from mechanism
    rather than demonstrated. Without a threshold, and without a
    drug-class-specific test, the relation informs reasoning but does not yet
    support a decision rule.
  proposed_experiments:
  - experiment_id: residual_activity_response_threshold_study
    name: Prospective genotype-stratified response study with quantified residual receptor activity
    description: >-
      In a homozygous and compound-heterozygous FH cohort, measure residual
      LDLR activity for each proband's allele pair in a standardized cell-based
      uptake assay, then relate that quantity to the achieved LDL-C reduction
      on a high-intensity statin and, separately, on a PCSK9 monoclonal
      antibody. The readout is whether a single activity threshold predicts
      response for both drug classes or whether the classes have different
      thresholds.
- discussion_id: ldlr_model_arterial_translation
  kind: HUMAN_MODEL_MISMATCH
  attaches_to:
  - "pathophysiology#Premature Atherosclerotic Cardiovascular Events"
  prompt: >-
    Does the arterial disease of any available LDLR-deficient animal model
    reproduce the human course closely enough to test interventions aimed at
    events rather than at LDL levels?
  rationale: >-
    The clearance defect translates cleanly across species - the Ldlr-/- mouse
    reproduces it and adenoviral receptor restoration reverses it - but the
    arterial arm does not. Murine lipoprotein metabolism is apoB48- and
    HDL-dominated, so the mouse does not reach human homozygous-FH cholesterol
    levels and develops limited spontaneous atherosclerosis on chow. The WHHL
    rabbit is far closer in lipoprotein physiology and does develop coronary
    disease, but the strain history reports that lesion rupture there requires
    secondary mechanical forces such as spasm, so it is not a clean analogue of
    spontaneous human plaque rupture. The genome-edited LDLR-knockout
    cynomolgus monkey reaches human-like lipid levels and develops xanthoma
    within a year, but the published cohort is six founder animals with short
    follow-up and possible editing mosaicism. Each model is informative for the
    node it was curated against and none is currently adequate for
    event-endpoint intervention studies.
  proposed_experiments:
  - experiment_id: cross_species_plaque_rupture_comparison
    name: Cross-species comparison of plaque composition and rupture triggers under matched cumulative LDL exposure
    description: >-
      Compare coronary and aortic lesion composition, fibrous cap thickness,
      and spontaneous versus provoked rupture between LDLR-deficient rabbits,
      LDLR-knockout primates, and human FH imaging cohorts matched on
      cumulative LDL-C exposure rather than on age, to establish which model,
      if any, supports event-level extrapolation.

📚

References & Deep Research

References

1

PMID:24404629

Familial Hypercholesterolemia.

5 findings

Clinical characteristics. GeneReviews describes the FH clinical spectrum that LDLR-related FH defines - premature atherosclerotic plaque in the coronary arteries and proximal aorta, angina and myocardial infarction, tendon xanthoma, xanthelasma, and early corneal arcus, with calcific aortic valve disease and childhood-onset coronary artery disease in biallelic disease. The chapter covers FH as a class across LDLR, APOB and PCSK9, so it is class-level rather than LDLR-specific evidence and is cited as such throughout this entry.

"increases the risk of premature cardiovascular events such as angina and myocardial infarction"

Diagnosis and testing. GeneReviews gives the untreated LDL-C thresholds for a clinical FH diagnosis and names LDLR as one of three molecular routes to FH - the receptor-side route that defines this entry.

"The molecular diagnosis of FH can be established by identification of heterozygous or biallelic pathogenic variants in APOB (variants that impair binding of LDL-C to the LDL receptor), LDLR, or PCSK9 (gain of function); or rarely, identification of biallelic pathogenic variants in LDLRAP1."

Management. GeneReviews sets out lipid surveillance from age two years, statin initiation in children from around age eight, cardiovascular risk-factor modification, and the contraindication of statins in pregnancy.

"Monitor lipid levels from age two years"

Agents and circumstances to avoid. GeneReviews names the exposures that compound the arterial risk conferred by the receptor defect.

"Agents/circumstances to avoid: Smoking, high intake of saturated and trans unsaturated fat, sedentary lifestyle, obesity, hypertension, and diabetes mellitus."

Genetic counseling. GeneReviews states the autosomal dominant transmission risk that applies to LDLR-related FH and the more severe, earlier-onset presentation of biallelic disease.

"Each child of an individual with a heterozygous pathogenic variant in APOB, LDLR, or PCSK9 has a 50% chance of inheriting the pathogenic variant and having FH."

Deep Research

1

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Evaluations and curation notes (2)

Augment: LDLR-Related Familial Hypercholesterolemia (MONDO:0007750) · 2026-09-06T14:36:37Z · View source

Augmentation of the existing FH1 entry, requested as 'hypercholesterolemia, familial, 1'. Duplicate preflight found MONDO:0007750 already curated here (created by PR #8971); no open PR or issue covered it, so this edits the existing entry rather than creating a new one. Deep research: fresh falcon (Edison) run, 2026-09-06, 682s, 51 citations, replacing the 2026-08-19 report in place. Its own validation reports 16/16 references resolved, confabulation_rate 0.0, 2/2 checkable quotes valid, 0 off topic; 32/33 terms resolved with 0 unresolved. needs_review is true for one item only: the report writes 'if available' and 'association score 0.877' beside MONDO:0007750, a table-parsing artifact rather than a mis-binding, and the CURIE is the correct one for this entry. The report's single unverifiable quote (DOI:10.1056/NEJMoa1816454, no abstract exposed) was resolved by fetching the PubMed record instead: PMID:31618540 carries the sentence verbatim, and that PMID is what is cited here. just preflight-dr returns SKIP because MONDO records no RO:0004003 causal gene for MONDO:0007750, as the entry's notes already record. Manual fallback confirms the entity: OMIM 143890 on both sides, and gene mentions LDLR=99 against PCSK9=21 and APOB=7, so the report is receptor-side FH1 and not a sibling entry. Added, chosen to bring this entry to parity with its closest sibling Autosomal_Dominant_Hypercholesterolemia_3 and to serve the entry's allelic-series thesis: - experimental_models (4, new section). The J.D. fibroblast strain (PMID:189940), which is where the receptor classes were defined and which the entry's Class 4 variant description already named without citing; JD iPSC-derived hepatocytes (PMID:22653811), the same patient genotype moved into the cell type that clears plasma LDL, carrying the lovastatin non-response that reads out the residual-activity gating node; the CHO-ldlA7 heterologous assay (PMID:34167030), which is the assay behind the entry's existing Functional Characterization of LDLR Variants diagnosis item; and the activity-normalized prime-editing saturation screen of 5,184 coding variants (PMID:42677454). - datasets (3, new section, previously 0 percent). geo:GSE329001 (the prime-editing screen, LDLR-specific), geo:GSE126352 and geo:GSE178126. All three relevance-triaged by hand; the two clinical cohorts are recorded in their descriptions as class-level because neither series reports LDLR genotypes. Verified with just verify-datasets (3/3 OK) and the GEO_*.md cache files are committed. - environmental (2, new section). Saturated/trans fat and tobacco smoking, both linked into the pathograph, attached to the nodes they actually act on: diet to Lifelong Elevation of Plasma LDL Cholesterol, smoking to Endothelial Dysfunction and Subendothelial LDL Retention, since smoking does not raise LDL. Substantiated from GeneReviews (PMID:24404629) plus the UK Biobank lifestyle-interaction study (PMID:35294538), whose explanation records that its 4-point score bundles four exposures and pools carriers across LDLR, APOB and PCSK9. - treatments. Two evidence items on statin therapy from the 20-year paediatric follow-up (PMID:31618540), including the residual burden the same study reports (mean LDL-C fell 32 percent, 20 percent reached goal), so the outcome claim is not read as corrected receptor function. Also corrected three pieces of stale prose that named supports: PARTIAL, an enum value retired in #10003 and no longer present anywhere in this file's data. The four new GeneReviews evidence items were re-graded from HUMAN_CLINICAL to OTHER to follow the evidence_source convention this entry documents in its own notes for the chapter's Management and Agents-to-Avoid sections; check-snippet-grading was what surfaced the divergence. Deliberately not added: model-level evidence on the four experimental models, matching this file's existing animal_models, which carry their evidence on the links and readouts where the claims actually sit. Validation: just validate passes (schema, terms, 144/144 snippets verified); just validate-disorders (the batched gate CI runs) passes; just verify-datasets 3/3; check-entity-refs, check-causal-targets, check-duplicate-keys, check-qualifier-terms, check-folded-hyphens, check-snippet-length, check-title-snippets, check-snippet-grading, check-environmental-evidence and check-enum-values all pass. Compliance 92.5 percent (333/360), up from 285/306 in absolute terms; the percentage is flat because dataset records carry no evidence block by the dataset-curation SOP.

Create: LDLR-Related Familial Hypercholesterolemia (MONDO:0007750, FH1) · 2026-08-19T16:10:45Z · View source

Curated hypercholesterolemia, familial, 1 (MONDO:0007750; OMIM:143890) as a standalone Disease entry - the LDLR/receptor-side member of the dominant FH trio. Scope decision (the crux of issue #8765). Curated separately rather than folded into kb/disorders/Familial_Hypercholesterolemia.yaml (MONDO:0005439), for four reasons: (1) MONDO models MONDO:0007750 as a distinct is_a child of MONDO:0005439, anchored on OMIM:143890 and the synonym "LDL receptor disorder"; (2) the umbrella entry's has_subtypes axis is zygosity (heterozygous / homozygous), not gene, so a gene-defined entity cannot be attached there without mixing two orthogonal axes; (3) the two other dominant FH genes already have sibling entries curated on exactly this rationale - Familial_Defective_Apolipoprotein_B-100 (MONDO:0007751, APOB) and Autosomal_Dominant_Hypercholesterolemia_3 (MONDO:0011369, PCSK9) - so leaving the receptor-side form unmodelled would make the set incoherent; and (4) the mechanism graph curated here is the LDLR receptor itinerary (synthesis, ER-to- Golgi export, surface ligand binding, clathrin-pit clustering, endosomal release and recycling) with the classical mutation classes mapped onto the step each breaks, plus the residual-activity-gates-receptor-dependent-therapy relation. The umbrella entry does not model any of that. The entry states this explicitly in its notes: block so the added value over MONDO:0005439 is on the record. NEC check. 'just preflight-dr' returned SKIP: MONDO records no RO:0004003 causal gene for this term, so the automated gene-identity check cannot discriminate and the manual OMIM/gene/synonym preflight was used instead. The report's OMIM (143890) matches the MONDO OMIM xref; LDLR dominates the report's gene mentions (LDLR=70 vs PCSK9=19, APOB=3); and the MONDO synonym list ("LDL receptor disorder", FHCL1, "hyperlipoproteinemia, type 2A") is uniformly receptor-side. Identity confirmed as the LDLR form, not ADH2 (APOB) or ADH3 (PCSK9). Deep research. Provider: falcon. The report's own reference-validation pass resolved 7/7 extracted identifiers with 0 unresolved, 0 unverifiable, and 0 off-topic, so nothing was curated from an unresolved citation. GeneReviews baseline. PMID:24404629 (Familial Hypercholesterolemia) fetched, cached, tagged GeneReviews in the top-level references: block, and mined into structured findings covering clinical characteristics, diagnosis/testing, management, agents and circumstances to avoid, and genetic counselling. The chapter is class-level across LDLR/APOB/PCSK9 and is cited as such rather than as LDLR-specific evidence. Validation actually run and read. 'just validate' passed end to end - schema validation, term validation, and reference validation with "Snippets checked: 106/106 verified against cached references". 'just validate-disorders' (the batched pre-PR sweep CI runs, --no-full-text) passed on this file. 'just check-duplicate-keys' clean. 'just check-title-snippets --against-ref origin/main' reported no new title-quoting snippets. tests/test_data.py passed for this file (16 scoped tests; the one suite-wide failure is a pre-existing bare -URL reference issue in Travelers_Diarrhea.yaml, untouched by this branch). Weighted compliance 92.3 percent. Pre-PR self-review round (red-team pass before opening the PR). A reviewer agent run against the draft returned REQUEST_CHANGES; every finding was acted on rather than argued away: - CRITICAL, fixed. The draft asserted in three places that statins "fail in receptor-negative (null-null) homozygotes". The only genotype-stratified evidence in the entry is an 8-patient trial of a PCSK9 antibody (PMID:24014831), whose two receptor-negative patients were already on stable statin therapy at enrolment - and the entry's own cited review reports statins helping both homozygous and heterozygous patients. The claim was restricted to the agent actually tested, and the untested statin arm was added to the residual_ldlr_activity_response_threshold KNOWLEDGE_GAP, which is its proper home. - Six evidence items quoted methods, aims, or boilerplate rather than findings (the #8352 failure family). Four were replaced with the actual result sentences, which were already present in the cached references - notably substituting "16 of the 132 cell strains (12%) synthesized no immunodetectable LDL receptor protein" for the immunoprecipitation methods sentence. - The class 3 (binding-defective) node's lead snippet was a proportion claim about the EGF-precursor domain, which in context supports the class 2 and class 5 nodes rather than class 3. Replaced with the binding-specific finding ("similar expression to wt LDLR but demonstrated deficient LDL binding"). - Four treatments every sibling entry curates were missing and are now added: ezetimibe, bempedoic acid, inclisiran, and liver transplantation. Three are load-bearing for this entry's thesis rather than incidental - ezetimibe and bempedoic acid both lower LDL-C by upregulating LDL receptor, so they attach to the receptor-dependent gating node, and liver transplantation is the limiting case of supplying receptor and attaches directly to the receptor- activity node. Note this entry deliberately does NOT follow the umbrella entry's characterization of ezetimibe as "independent of LDLR"; the cited review states it works through a compensatory increase in LDL receptor, and the divergence is recorded in that treatment's notes. - Added a differential_diagnoses block (APOB / PCSK9 / LDLRAP1 recessive / polygenic / Lp(a)-mimicry / sitosterolemia-dysbetalipoproteinemia-CESD), which for an entry whose whole rationale is separating the receptor-side form from its siblings was the highest-value structured gap. - Added the on-thesis trial NCT06597006 (inclisiran in children with documented biallelic null LDLR mutations, excluding poor prior PCSK9-antibody responders), whose enrolment criteria operationalize the gating relation. - Softened the lomitapide genotype claim: unlike the evinacumab trial, the pivotal lomitapide study was single-arm and not genotype-stratified. - Added plasma apolipoprotein B as a biochemical marker, and replaced the lipoprotein(a) biomarker term with the neutral HP:0430148 so it no longer reads as "variably elevated-Lp(a)". NOTE: the reviewer proposed HP:0012185 for apolipoprotein B; OAK shows HP:0012185 is "Constrictive median neuropathy", so that suggestion was discarded and HP:0031798 verified and used instead - reviewer suggestions were term-checked rather than trusted. - Documented, rather than flattened, the mixed evidence_source values against the GeneReviews PMID: Clinical Characteristics/Diagnosis/Genetic Counseling statements are HUMAN_CLINICAL observations, Management and Agents-to-Avoid statements are expert recommendations and are OTHER. Post-review validation (all re-run and read after the changes): just validate-disorders passed with "Snippets checked: 123/123 verified against cached references"; just validate-terms passed; check-duplicate-keys clean; check-title-snippets reports no new title-quoting snippets; 16 scoped tests/test_data.py tests pass. Weighted compliance rose from 92.3 to 93.4 percent. Known gaps left open deliberately: the two discussions: entries (a KNOWLEDGE_GAP on what residual-receptor-activity threshold separates responders from non- responders to receptor-directed therapy, and a HUMAN_MODEL_MISMATCH on whether any LDLR-deficient animal model reproduces the human arterial course well enough for event-endpoint studies) carry proposed_experiments but no evidence, which is correct for open questions.

Falcon ▸

Disease Characteristics Research Template

Edison Scientific Literature 51 citations 2026-09-06T14:20:32.104217

Question: You are an expert researcher providing comprehensive, well-cited information.

Provide detailed information focusing on: 1. Key concepts and definitions with current understanding 2. Recent developments and latest research (prioritize 2023-2024 sources) 3. Current applications and real-world implementations 4. Expert opinions and analysis from authoritative sources 5. Relevant statistics and data from recent studies

Format as a comprehensive research report with proper citations. Include URLs and publication dates where available. Always prioritize recent, authoritative sources and provide specific citations for all major claims.

Disease Characteristics Research Template

Target Disease

Disease Name: LDLR-Related Familial Hypercholesterolemia
MONDO ID: MONDO:0007750 (if available)
Category: Mendelian

Research Objectives

Please provide a comprehensive research report on LDLR-Related Familial Hypercholesterolemia covering all of the disease characteristics listed below. This report will be used to populate a disease knowledge base entry. Be thorough and cite primary literature (PMID preferred) for all claims.

For each section, suggested databases/resources are listed. These are the first places you should search for information on each topic.

1. Disease Information

Search first: OMIM, Orphanet, ICD-10/ICD-11, MeSH, PubMed

What is the disease? Provide a concise overview.
What are the key identifiers? (OMIM, Orphanet, ICD-10/ICD-11, MeSH, Mondo)
What are the common synonyms and alternative names?
Is the information derived from individual patients (e.g., EHR) or aggregated disease-level resources?

2. Etiology

Disease Causal Factors: What are the primary causes? (genetic, environmental, infectious, mechanistic)
Risk Factors:

Search first: PubMed, Cochrane Library, UpToDate, clinical guidelines, ClinVar, ClinGen, GWAS Catalog, PheGenI, CTD, CDC, WHO, epidemiological databases
Genetic risk factors (causal variants, susceptibility loci, modifier genes)
Environmental risk factors (toxins, lifestyle, occupational exposures, age, sex, family history)
Protective Factors:

Search first: PubMed, Cochrane Library, clinical trial databases, GWAS Catalog, gnomAD, WHO, CDC, nutrition databases
Genetic protective factors (protective variants, modifier alleles)
Environmental protective factors (diet, lifestyle, exposures that reduce risk)
Gene-Environment Interactions: How do genetic and environmental factors interact to influence disease?

Search first: CTD, PubMed, PheGenI, GxE databases

3. Phenotypes

Search first: HPO (Human Phenotype Ontology), OMIM, Orphanet, PubMed, clinicaltrials.gov, MedDRA, SNOMED CT, DECIPHER, LOINC

For each phenotype, provide: - Phenotype type: symptoms, clinical signs, physical manifestations, behavioral changes, or laboratory abnormalities

For symptoms/signs: HPO, OMIM, Orphanet, PubMed For behavioral changes: HPO, DSM, RDoC (Research Domain Criteria), PubMed For laboratory abnormalities: LOINC, SNOMED CT, LabTests Online, PubMed - Phenotype characteristics: Search first: OMIM, Orphanet, HPO, PubMed - Age of symptom onset (neonatal, childhood, adult-onset, late-onset) - Symptom severity (mild, moderate, severe, variable) - Symptom progression (stable, progressive, episodic, fluctuating) - Frequency among affected individuals (percentage or qualitative) - Quality of life impact: Effects on daily functioning and well-being (per-phenotype when possible) Search first: EQ-5D database, SF-36, WHO QOL databases, PubMed - Suggest HPO (Human Phenotype Ontology) terms for each phenotype

4. Genetic/Molecular Information

Causal Genes: Gene mutations or chromosomal abnormalities responsible for disease (gene symbols, OMIM IDs)

Search first: OMIM, ClinVar, HGMD, Ensembl, NCBI Gene
Pathogenic Variants:
Affected genes (gene symbols, HGNC IDs) > Search first: OMIM, NCBI Gene, Ensembl, HGNC, UniProt, GeneCards
Variant classification (pathogenic, likely pathogenic, VUS per ACMG/AMP guidelines) > Search first: ClinVar, ClinGen, ACMG/AMP guidelines, VarSome
Variant type/class (missense, frameshift, nonsense, splice-site, structural)
Allele frequency in population databases > Search first: gnomAD, 1000 Genomes, ExAC, TOPMed, dbSNP
Somatic vs germline origin > Search first: COSMIC (somatic), ClinVar, ICGC, TCGA
Functional consequences (loss of function, gain of function, dominant negative)
Modifier Genes: Genes that modify disease severity or expression
Epigenetic Information: DNA methylation, histone modifications, chromatin changes affecting disease

Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth
Chromosomal Abnormalities: Large-scale genetic changes (aneuploidy, translocations, inversions)

Search first: DECIPHER, ClinVar, ECARUCA, UCSC Genome Browser

5. Environmental Information

Environmental Factors: Non-genetic contributing factors (toxins, radiation, pollution, occupational exposure)

Search first: CTD (Comparative Toxicogenomics Database), TOXNET, PubMed, EPA databases
Lifestyle Factors: Behavioral factors (smoking, diet, exercise, alcohol consumption)

Search first: CDC databases, WHO, PubMed, NHANES
Infectious Agents: If applicable, pathogens causing or triggering disease (bacteria, viruses, fungi, parasites)

Search first: NCBI Taxonomy, ViPR, BV-BRC, MicrobeDB, GIDEON

6. Mechanism / Pathophysiology

Present this section as an ordered causal chain first, then the detail below. Open with a numbered sequence of mechanistic steps running from the initiating lesion (mutation, exposure, infection) to the clinical manifestation, one step per line, each naming what it causes next. State the causal verb explicitly ("leads to", "results in") and say where a step is inferred rather than demonstrated. Where the mechanism branches, show the branch. The categories below are a checklist of what to cover within those steps, not the organizing structure — a step may draw on several of them, and a category may contribute to several steps.

Molecular Pathways: Specific signaling cascades or biochemical pathways involved (Wnt, MAPK, mTOR, PI3K-AKT, etc.)

Search first: KEGG, Reactome, WikiPathways, PathBank, BioCyc
Cellular Processes: Cell-level mechanisms (apoptosis, autophagy, cell cycle dysregulation, inflammation, etc.)

Search first: Gene Ontology (GO), Reactome, KEGG, PubMed
Protein Dysfunction: How protein structure or function is altered (misfolding, aggregation, loss of function, gain of function)

Search first: UniProt, PDB (Protein Data Bank), InterPro, Pfam, AlphaFold
Metabolic Changes: Alterations in metabolic processes (energy metabolism, lipid metabolism, amino acid metabolism)

Search first: KEGG, BioCyc, HMDB (Human Metabolome Database), BRENDA
Immune System Involvement: Role of immune response (autoimmunity, immunodeficiency, chronic inflammation)

Search first: ImmPort, Immunome Database, IEDB, Gene Ontology
Tissue Damage Mechanisms: How tissues/ are injured (oxidative stress, ischemia, fibrosis, necrosis)

Search first: PubMed, Gene Ontology, Reactome
Biochemical Abnormalities: Specific molecular defects (enzyme deficiencies, receptor dysfunction, ion channel defects)

Search first: BRENDA, UniProt, KEGG, OMIM, PubMed
Epigenetic Changes: DNA methylation, histone modifications affecting gene expression in disease

Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth
Molecular Profiling (if available):
Transcriptomics/gene expression changes > Search first: GEO (Gene Expression Omnibus), ArrayExpress, GTEx, Human Cell Atlas, SRA
Proteomics findings > Search first: PRIDE, ProteomeXchange, Human Protein Atlas, STRING, BioGRID
Metabolomics signatures > Search first: MetaboLights, Metabolomics Workbench, HMDB, METLIN
Lipidomics alterations > Search first: LIPID MAPS, SwissLipids, LipidHome, Metabolomics Workbench
Genomic structural features > Search first: UCSC Genome Browser, Ensembl, NCBI, dbVar, DGV
Advanced Technologies (if applicable):
Single-cell analysis findings (cell-type specific mechanisms, cellular heterogeneity) > Search first: Human Cell Atlas, Single Cell Portal, GEO, CELLxGENE
Spatial transcriptomics findings > Search first: GEO, Spatial Research, Vizgen, 10x Genomics data
Multi-omics integration results > Search first: TCGA, ICGC, cBioPortal, LinkedOmics, PubMed
Functional genomics screens (CRISPR, RNAi) > Search first: DepMap, GenomeRNAi, PubMed, BioGRID ORCS

For each mechanism, describe: - The causal chain from initial trigger to clinical manifestation - Which mechanisms are upstream vs downstream - What cell types and biological processes are involved - Suggest GO terms for biological processes and CL terms for cell types

7. Anatomical Structures Affected

Organ Level:
Primary organs directly affected
Secondary organ involvement (complications, secondary effects)
Body systems involved (cardiovascular, nervous, digestive, respiratory, endocrine, etc.)

Search first: Uberon, FMA (Foundational Model of Anatomy), OMIM, HPO, ICD-11, MeSH, SNOMED CT
Tissue and Cell Level:
Specific tissue types affected (epithelial, connective, muscle, nervous)
Specific cell populations targeted (with Cell Ontology terms)

Search first: Uberon, Human Protein Atlas, Cell Ontology, Human Cell Atlas, CellMarker, PanglaoDB
Subcellular Level:
Cellular compartments involved (mitochondria, nucleus, ER, lysosomes) (with GO Cellular Component terms)

Search first: Gene Ontology (Cellular Component), UniProt, Human Protein Atlas
Localization:
Specific anatomical sites (with UBERON terms) > Search first: FMA, Uberon, NeuroNames (for brain), SNOMED CT
Lateralization (unilateral, bilateral, asymmetric) > Search first: HPO, clinical literature, imaging databases

8. Temporal Development

Onset:
Typical age of onset (congenital, pediatric, adult, geriatric)
Onset pattern (acute, subacute, chronic, insidious)

Search first: OMIM, Orphanet, HPO, PubMed
Progression:
Disease stages (early, intermediate, advanced, end-stage) > Search first: Cancer Staging Manual (AJCC), WHO classifications, PubMed
Progression rate (rapid, slow, variable)
Disease course pattern (episodic, relapsing-remitting, progressive, stable)
Disease duration (self-limited, chronic lifelong)

Search first: Disease registries, longitudinal cohort databases, natural history studies, PubMed, Orphanet, OMIM
Patterns:
Remission patterns (spontaneous, treatment-induced) > Search first: Clinical trial databases, disease registries, PubMed
Critical periods (time windows of vulnerability or opportunity for intervention) > Search first: PubMed, developmental biology databases, clinical guidelines

9. Inheritance and Population

Epidemiology:
Prevalence (cases per 100,000 at given time)
Incidence (new cases per 100,000 per year)

Search first: Orphanet, CDC, WHO, GBD (Global Burden of Disease), national registries, SEER, disease registries
For Genetic Etiology:
Inheritance pattern (AD, AR, X-linked, mitochondrial, multifactorial, polygenic) > Search first: OMIM, Orphanet, ClinVar, GTR (Genetic Testing Registry)
Penetrance (complete, incomplete, age-dependent) > Search first: ClinVar, OMIM, PubMed, ClinGen
Expressivity (variable, consistent) > Search first: OMIM, ClinVar, PubMed
Genetic anticipation (increasing severity in successive generations) > Search first: OMIM, PubMed (especially for repeat expansion disorders)
Germline mosaicism > Search first: ClinVar, OMIM, genetic counseling literature, PubMed
Founder effects (population-specific mutations) > Search first: gnomAD, population genetics databases, PubMed
Consanguinity role > Search first: OMIM, population studies, genetic counseling resources
Carrier frequency > Search first: gnomAD, carrier screening databases, GeneReviews, GTR
Population Demographics:
Affected populations (ethnic or demographic groups with higher prevalence) > Search first: gnomAD, 1000 Genomes, PAGE Study, PubMed, population registries
Geographic distribution (endemic areas, regional variation) > Search first: WHO, CDC, GBD, Orphanet, geographic epidemiology databases
Geographic distribution of specific variants
Sex ratio (male:female) > Search first: Disease registries, OMIM, PubMed, epidemiological databases
Age distribution of affected individuals > Search first: CDC, disease registries, SEER, Orphanet

10. Diagnostics

Clinical Tests:
Laboratory tests (blood, urine, tissue chemistry, specific enzyme assays) > Search first: LOINC, LabTests Online, PubMed
Biomarkers (proteins, metabolites, genetic markers, circulating biomarkers) > Search first: FDA Biomarker List, BEST (Biomarkers, EndpointS, and other Tools), PubMed
Imaging studies (X-ray, CT, MRI, PET, ultrasound) > Search first: RadLex, DICOM, Radiopaedia, imaging databases
Functional tests (pulmonary function, cardiac stress tests) > Search first: LOINC, clinical guidelines, PubMed
Electrophysiology (EEG, EMG, ECG, nerve conduction studies) > Search first: LOINC, clinical neurophysiology databases, PubMed
Biopsy findings (histopathology, immunohistochemistry) > Search first: SNOMED CT, College of American Pathologists resources, PubMed
Pathology findings (microscopic examination) > Search first: SNOMED CT, Digital Pathology databases, PubMed
Genetic Testing:

Search first: GTR (Genetic Testing Registry), GeneReviews, ClinGen
Overview of recommended genetic testing approach
Whole genome sequencing (WGS) utility > Search first: GTR, ClinVar, GEL (Genomics England), gnomAD
Whole exome sequencing (WES) utility > Search first: GTR, ClinVar, OMIM, GeneMatcher
Gene panels (which panels, which genes) > Search first: GTR, ClinVar, laboratory-specific databases
Single gene testing > Search first: GTR, ClinVar, OMIM, GeneReviews
Chromosomal microarray (CMA) > Search first: DECIPHER, ClinVar, dbVar, ECARUCA
Karyotyping > Search first: Chromosome Abnormality Database, ClinVar, cytogenetics resources
FISH > Search first: ClinVar, cytogenetics databases, PubMed
Mitochondrial DNA testing > Search first: MITOMAP, MSeqDR, ClinVar, GTR
Repeat expansion testing > Search first: GTR, ClinVar, repeat expansion databases, PubMed
Omics-Based Diagnostics (if applicable):
RNA sequencing / transcriptomics > Search first: GEO, ArrayExpress, GTEx, RNA-seq databases
Proteomics > Search first: PRIDE, ProteomeXchange, FDA Biomarker database
Metabolomics > Search first: MetaboLights, Metabolomics Workbench, HMDB
Epigenomics > Search first: GEO, ENCODE, Roadmap Epigenomics, MethBase
Liquid biopsy > Search first: COSMIC, ClinVar, liquid biopsy databases, PubMed
Clinical Criteria:
Standardized diagnostic criteria (DSM, ICD, society guidelines) > Search first: DSM-5, ICD-11, clinical society guidelines, UpToDate
Differential diagnosis (other conditions to rule out, with distinguishing features) > Search first: DynaMed, UpToDate, clinical decision support systems
Screening:
Screening methods for asymptomatic individuals (newborn screening, carrier screening, cascade screening) > Search first: ACMG recommendations, CDC newborn screening, GTR

11. Outcome/Prognosis

Survival and Mortality:
Survival rate (5-year, 10-year, overall) > Search first: SEER, cancer registries, disease-specific registries, PubMed
Life expectancy (with and without treatment if applicable) > Search first: Orphanet, disease registries, actuarial databases, PubMed
Mortality rate > Search first: CDC, WHO, GBD, national mortality databases
Disease-specific mortality (deaths directly attributable to disease) > Search first: Disease registries, CDC Wonder, GBD, PubMed
Morbidity and Function:
Morbidity (disease-related disability and health impacts) > Search first: GBD, WHO, disability databases, PubMed
Disability outcomes (long-term functional impairments) > Search first: ICF (International Classification of Functioning), disability registries
Quality of life measures (EQ-5D, SF-36, PROMIS, disease-specific tools) > Search first: EQ-5D database, SF-36, PROMIS, PubMed
Disease Course:
Complications (secondary problems: infections, organ failure, etc.) > Search first: ICD codes, disease registries, clinical databases, PubMed
Recovery potential (likelihood and extent of recovery, with vs without treatment) > Search first: Natural history studies, rehabilitation databases, PubMed
Prediction:
Prognostic factors (age, disease severity, biomarkers, treatment response) > Search first: Prognostic models databases, clinical calculators, PubMed
Prognostic biomarkers (molecular markers predicting disease course) > Search first: FDA Biomarker database, PubMed, cancer prognostic databases

12. Treatment

Pharmacotherapy:
Pharmacological treatments (drug names, drug classes, mechanisms of action) > Search first: DrugBank, RxNorm, ATC classification, DailyMed, FDA databases
Pharmacogenomics (how genetic variants affect drug metabolism, efficacy, toxicity) > Search first: PharmGKB, CPIC (Clinical Pharmacogenetics), FDA Table of PGx Biomarkers
Advanced Therapeutics:
Gene therapy (viral vectors, CRISPR, gene replacement, gene editing) > Search first: ClinicalTrials.gov, FDA gene therapy database, ASGCT resources
Cell therapy (stem cell transplant, CAR-T, cellular therapeutics) > Search first: ClinicalTrials.gov, FDA cell therapy database, FACT standards
RNA-based therapies (ASOs, siRNA, mRNA therapies) > Search first: ClinicalTrials.gov, FDA approvals, PubMed
Targeted therapies (treatments directed at specific molecular targets) > Search first: My Cancer Genome, OncoKB, ClinicalTrials.gov, FDA approvals
Immunotherapies (checkpoint inhibitors, monoclonal antibodies) > Search first: Cancer Immunotherapy Database, FDA approvals, ClinicalTrials.gov
Surgical and Interventional:
Surgical interventions (types of surgery, timing, outcomes) > Search first: CPT codes, surgical registries, clinical guidelines, PubMed
Supportive and Rehabilitative:
Supportive care (symptom management, pain control, nutrition) > Search first: Clinical guidelines, Cochrane Library, PubMed
Rehabilitation (physical therapy, occupational therapy, speech therapy) > Search first: Rehabilitation medicine databases, clinical guidelines, PubMed
Experimental:
Experimental treatments in clinical trials (with NCT identifiers if available) > Search first: ClinicalTrials.gov, EU Clinical Trials Register, WHO ICTRP
Treatment Outcomes:
Treatment response rates > Search first: Clinical trial databases, FDA reviews, systematic reviews, PubMed
Side effects and adverse events > Search first: FDA Adverse Event Reporting System (FAERS), MedWatch, PubMed
Treatment Strategy:
Treatment algorithms (clinical pathways, decision trees) > Search first: Clinical practice guidelines, NCCN Guidelines, UpToDate
Combination therapies > Search first: ClinicalTrials.gov, treatment guidelines, PubMed
Personalized medicine approaches (genotype-guided treatment) > Search first: My Cancer Genome, CIViC, PharmGKB, precision medicine databases

For each treatment, suggest NCIT (NCI Thesaurus) clinical-intervention terms where applicable.

13. Prevention

Prevention Levels:
Primary prevention (preventing disease occurrence: vaccination, risk factor modification) > Search first: CDC, WHO, USPSTF recommendations, Cochrane Library
Secondary prevention (early detection and treatment: screening programs, early intervention) > Search first: USPSTF, CDC screening guidelines, WHO
Tertiary prevention (preventing complications in those with disease) > Search first: Clinical guidelines, disease management protocols, PubMed
Immunization: Vaccine strategies (if applicable)

Search first: CDC vaccine schedules, WHO immunization, FDA vaccine database
Screening and Early Detection:
Screening programs (population-based: newborn screening, cancer screening) > Search first: CDC screening programs, USPSTF, cancer screening databases
Genetic screening (carrier screening, preimplantation genetic diagnosis, prenatal testing) > Search first: ACMG recommendations, ACOG guidelines, GTR
Risk stratification (identifying high-risk individuals for targeted prevention) > Search first: Risk prediction models, clinical calculators, PubMed
Behavioral Interventions: Lifestyle modifications to reduce risk

Search first: CDC, WHO, behavioral intervention databases, Cochrane Library
Counseling: Genetic counseling (risk assessment, family planning guidance)

Search first: NSGC resources, ACMG guidelines, GeneReviews
Public Health:
Public health interventions (sanitation, vector control, health education) > Search first: CDC, WHO, public health databases, PubMed
Environmental interventions (reducing environmental risk factors) > Search first: EPA databases, WHO environmental health, PubMed
Prophylaxis: Preventive medications or procedures

Search first: Clinical guidelines, FDA approvals, PubMed

14. Other Species / Natural Disease

Taxonomy: Species affected (with NCBI Taxon identifiers)

Search first: NCBI Taxonomy
Breed: Specific breeds affected (with VBO identifiers if applicable)

Search first: VBO (Vertebrate Breed Ontology)
Gene: Orthologous genes in other species (with NCBI Gene IDs)

Search first: NCBI Gene
Natural Disease:
Naturally occurring disease in other species (companion animals, wildlife) > Search first: OMIA (Online Mendelian Inheritance in Animals), VetCompass, PubMed
Veterinary relevance and importance in animal health > Search first: OMIA, veterinary databases, PubMed
Comparative Biology:
Comparative pathology (similarities and differences across species) > Search first: OMIA, comparative pathology databases, PubMed
Evolutionary conservation of disease mechanisms > Search first: HomoloGene, OrthoMCL, Alliance of Genome Resources
Transmission (if applicable):
Zoonotic potential > Search first: CDC zoonotic diseases, WHO zoonoses, GIDEON
Cross-species susceptibility > Search first: NCBI Taxonomy, veterinary databases, PubMed

15. Model Organisms

Model Types:
Model organism type (mammalian, invertebrate, cellular, in vitro) > Search first: Alliance of Genome Resources, model organism databases
Specific model systems (mouse, rat, zebrafish, Drosophila, C. elegans, yeast, cell lines, organoids, iPSCs) > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, SGD, ATCC, Cellosaurus
Induced models (drug treatment, surgical intervention, environmental manipulation) > Search first: MGI, model organism databases, PubMed
Genetic Models:
Types available (knockout, knock-in, transgenic, conditional, humanized) > Search first: MGI, IMPC, KOMP, EuMMCR, IMSR
Model Characteristics:
Phenotype recapitulation (how well model reproduces human disease features) > Search first: Model organism databases, comparative studies, PubMed
Model limitations (aspects of human disease not captured) > Search first: Model organism databases, PubMed, review articles
Applications:
Research applications (what aspects of disease can be studied) > Search first: Model organism databases, PubMed
Resources:
Model databases > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, IMSR, EMMA, MMRRC

Citation Requirements

Cite primary literature (PMID preferred) for all mechanistic and clinical claims
Prioritize recent reviews and landmark papers
Include direct quotes from abstracts where possible to support key statements
Distinguish evidence source types: human clinical, model organism, in vitro, computational

Output Format

Structure your response as a comprehensive narrative organized by the sections above. For each section, provide: - Factual content with specific details (numbers, percentages, gene names, variant nomenclature) - Ontology term suggestions (HPO, GO, CL, UBERON, CHEBI, NCIT, MONDO) where applicable - Evidence citations with PMIDs - Direct quotes from abstracts to support key claims - Clear indication when information is not available or not applicable for this disease

This report will be used to populate a disease knowledge base entry with: - Pathophysiology descriptions with causal chains - Gene/protein annotations (HGNC, GO terms) - Phenotype associations (HP terms) with frequencies - Cell type involvement (CL terms) - Anatomical locations (UBERON terms) - Chemical entities (CHEBI terms) - Treatment annotations (NCIT terms) - Evidence items with PMIDs and exact abstract quotes - Epidemiology, prognosis, diagnostic, and prevention information - Animal model descriptions with phenotype recapitulation details

LDLR-Related Familial Hypercholesterolemia

Scope and evidence conventions

This report concerns familial hypercholesterolemia type 1 caused by germline pathogenic variants in LDLR, not the broader phenotypic category that also includes APOB-, PCSK9-, APOE-, and LDLRAP1-related disease or polygenic hypercholesterolemia. Many epidemiologic and therapeutic studies enroll clinical FH or HoFH without reporting gene-specific results; these are explicitly labeled broad-FH evidence and should not be entered as LDLR-specific penetrance or treatment estimates.

The evidence base consists principally of aggregated disease resources, human cohorts and trials, recent authoritative reviews, and model-organism studies—not individual-patient EHR data. The principal recent sources are Di Taranto and Fortunato (published 6 February 2023; DOI 10.3390/ijms24043224), Abifadel and Boileau (2023; DOI 10.1111/joim.13577), Fularski et al. (January 2024; DOI 10.3390/ijms25031637), and the 2024 pediatric PCSK9-inhibitor meta-analysis (published 8 October 2024; DOI 10.3390/medicina60101646). (fularski2024unveilingfamilialhypercholesterolemia—review pages 2-4, taranto2023geneticheterogeneityof pages 1-2, abifadel2023geneticandmolecular pages 1-2, xiao2024efficacyandsafety pages 1-2)

Domain	Key knowledge-base fact/statistic	Evidence type and scope	Source/date	DOI or URL
Identity	LDLR-related familial hypercholesterolemia 1 is MONDO:0007750; LDLR is the strongest associated target in the retrieved Open Targets record (score 0.877).	Aggregated disease-target evidence; LDLR-specific.	Open Targets, accessed 2026-09-06 (OpenTargets Search: familial hypercholesterolemia-LDLR)	https://platform.opentargets.org/
Prevalence	Broad HeFH prevalence estimates cluster near 1:250-1:313. These figures include non-LDLR forms of FH.	Meta-analysis and review; broad FH, so application to LDLR-related disease is approximate.	Di Taranto and Fortunato, Feb 2023; Humphries and Futema, Apr 2025 (humphries2025geneticdeterminantsof pages 1-2, taranto2023geneticheterogeneityof pages 1-2)	https://doi.org/10.3390/ijms24043224; https://doi.org/10.1111/ahg.12594
Causal contribution	Pathogenic LDLR variants account for approximately 90-95% of monogenic FH in cited reviews; estimates vary with ascertainment and testing strategy.	Aggregated genetic evidence; LDLR-specific attribution within broad monogenic FH.	Fularski et al., Jan 2024; Kalwick and Roth, Feb 2025 (fularski2024unveilingfamilialhypercholesterolemia—review pages 2-4, kalwick2025acomprehensivereview pages 1-3)	https://doi.org/10.3390/ijms25031637; https://doi.org/10.3390/nu17040659
Inheritance	One germline pathogenic LDLR allele generally causes heterozygous FH; two pathogenic alleles cause homozygous or compound-heterozygous LDLR-FH. Each child of a heterozygote has an approximately 50% chance of inheriting the variant.	Human genetic evidence; LDLR-specific, although HoFH can also arise from other genes.	Abifadel and Boileau, Oct 2023; Fularski et al., Jan 2024 (fularski2024unveilingfamilialhypercholesterolemia—review pages 2-4, fularski2024unveilingfamilialhypercholesterolemia—review pages 4-5, abifadel2023geneticandmolecular pages 1-2)	https://doi.org/10.1111/joim.13577; https://doi.org/10.3390/ijms25031637
Variant classes	LDLR defects can impair receptor synthesis or transport, LDL binding, clathrin-mediated internalization, or receptor recycling. Null alleles abolish function and generally produce more severe disease than receptor-defective alleles. Copy-number changes may constitute about 10% of causal variants; deep-intronic variants may require WGS.	Molecular and genetic review; LDLR-specific, but the 10% estimate is cohort-dependent.	Fularski et al., Jan 2024 (fularski2024unveilingfamilialhypercholesterolemia—review pages 2-4, fularski2024unveilingfamilialhypercholesterolemia—review pages 4-5)	https://doi.org/10.3390/ijms25031637
Mechanism	Reduced hepatocyte-surface LDLR activity impairs receptor-mediated LDL uptake, elevates LDL-C from birth, and increases cumulative arterial LDL exposure. PCSK9-mediated lysosomal degradation further reduces LDLR recycling.	Established molecular mechanism; LDLR-specific, with PCSK9 acting as a pathway regulator.	Fularski et al., Jan 2024; Abifadel and Boileau, Oct 2023 (fularski2024unveilingfamilialhypercholesterolemia—review pages 4-5, abifadel2023geneticandmolecular pages 1-2)	https://doi.org/10.3390/ijms25031637; https://doi.org/10.1111/joim.13577
Phenotypes	Core findings include lifelong elevated LDL-C, tendon or cutaneous xanthomas, xanthelasma, corneal arcus, progressive premature atherosclerosis, coronary heart disease, and increased cardiovascular morbidity and mortality.	Clinical review; broad FH but strongly applicable to LDLR-FH.	Abifadel and Boileau, Oct 2023; Fularski et al., Jan 2024 (fularski2024unveilingfamilialhypercholesterolemia—review pages 2-4, abifadel2023geneticandmolecular pages 1-2)	https://doi.org/10.1111/joim.13577; https://doi.org/10.3390/ijms25031637
Severe natural history	In severe untreated HoFH, coronary disease and aortic stenosis may occur by age 20, death may occur by age 30, and myocardial infarction can occur before age 10.	Clinical review; broad HoFH and not restricted to biallelic LDLR disease.	Fularski et al., Jan 2024 (fularski2024unveilingfamilialhypercholesterolemia—review pages 4-5)	https://doi.org/10.3390/ijms25031637
Diagnosis	Diagnosis integrates repeated fasting LDL-C measurements, premature ASCVD or family history, tendon xanthomas or corneal arcus, and exclusion of secondary causes. Dutch Lipid Clinic Network categories are definite above 8, probable 6-8, and possible 3-5 points.	Clinical diagnostic framework; broad FH.	Fularski et al., Jan 2024 (fularski2024unveilingfamilialhypercholesterolemia—review pages 2-4)	https://doi.org/10.3390/ijms25031637
Molecular testing	Testing should include LDLR and other canonical FH genes plus deletion-duplication analysis; WGS can identify deep-intronic or structural variants. A negative test does not exclude clinical FH.	Clinical genetics review; LDLR testing within a broad FH differential.	Fularski et al., Jan 2024; Humphries and Futema, Apr 2025 (fularski2024unveilingfamilialhypercholesterolemia—review pages 2-4, humphries2025geneticdeterminantsof pages 1-2)	https://doi.org/10.3390/ijms25031637; https://doi.org/10.1111/ahg.12594
Cascade screening	Once a familial pathogenic variant is known, first-degree relatives should receive targeted variant testing and lipid measurement; their prior risk is approximately 50% under dominant inheritance.	Guideline and review evidence; LDLR-specific when the familial variant is in LDLR.	Fularski et al., Jan 2024; Abifadel and Boileau, Oct 2023 (fularski2024unveilingfamilialhypercholesterolemia—review pages 2-4, abifadel2023geneticandmolecular pages 1-2)	https://doi.org/10.3390/ijms25031637; https://doi.org/10.1111/joim.13577
Screening implementation	Childhood programs reported approximately 91% acceptance among Slovenian five-year-olds using opt-out screening and approximately 60% participation in a West Virginia school program.	Real-world implementation summarized in a review; broad FH.	Gidding, Oct 2023 (gidding2023childhoodscreeningfor pages 4-6)	https://doi.org/10.1016/j.jacc.2023.07.028
Pediatric statins	A 20-year cohort of 214 children reported mean LDL-C reduction from 237.3 to 160.7 mg/dL, or 32%; 20% attained LDL-C below 100 mg/dL. By age 39, cardiovascular events were 1% versus 26% and cardiovascular death was 0% versus 7% compared with affected parents.	Human longitudinal cohort; broad genetically confirmed FH and probably predominantly LDLR, but not exclusively LDLR-specific.	Luirink et al., Oct 2019	https://doi.org/10.1056/NEJMoa1816454
Pediatric PCSK9 antibodies	A 2024 meta-analysis of nine studies, including three RCTs with 320 children, found LDL-C reduction of 37.92% (95% CI 32.78-43.06), apoB reduction of 33.67%, and Lp(a) reduction of 16.94%. Responses were consistent in HeFH but highly variable in HoFH.	Systematic review and meta-analysis; broad pediatric FH; treatment is mechanistically LDLR-dependent.	Xiao et al., Oct 8, 2024 (xiao2024efficacyandsafety pages 5-8, xiao2024efficacyandsafety pages 1-2, xiao2024efficacyandsafety pages 4-5)	https://doi.org/10.3390/medicina60101646
Apheresis	One LDL-apheresis procedure conventionally lowers LDL-C by more than 60%. Weekly treatment can regress xanthomas, slow atherosclerosis, and improve survival; initiation before age 6-7 years is recommended for severe HoFH where available.	Clinical review and real-world practice; broad HoFH, not LDLR-specific.	Tokgozoglu and Kayikcioglu, Sep 2021 (tokgozoglu2021familialhypercholesterolemiaglobal pages 9-10)	https://doi.org/10.1007/s11886-021-01565-5
Lifestyle interaction	Among carriers of pathogenic variants in LDLR, APOB, or PCSK9, estimated CAD risk by age 75 ranged from 35% with a favorable lifestyle to 66% with an unfavorable lifestyle.	Human case-control and cohort evidence; broad FH-gene carriers, not LDLR-specific.	Fahed et al., Mar 2022	https://doi.org/10.1001/jamanetworkopen.2022.2687
Sex disparity	Across 25 real-world studies with 129,441 participants, women were less likely to receive lipid-lowering therapy (OR 0.74, 95% CI 0.66-0.85) or attain LDL-C below 2.5 mmol/L (OR 0.85, 95% CI 0.74-0.97); fixed-dose trial response did not differ by sex.	Systematic review and meta-analysis; broad FH, not LDLR-specific.	Iatan et al., Jul 2024 (iatan2024sexdifferencesin pages 8-8)	https://doi.org/10.1093/eurheartj/ehae417
Mouse model	Ldlr-null mice model impaired LDL clearance and diet-accelerated atherosclerosis, but murine lipoprotein metabolism differs from that of humans and a cholesterol-rich diet is often needed for severe disease.	Genetic model-organism evidence; LDLR-specific model, summarized from retrieved model literature.	Contemporary model reviews	https://www.informatics.jax.org/
Rabbit model	Naturally occurring LDLR-deficient Watanabe heritable hyperlipidemic rabbits and the WHHLMI strain develop LDL-rich hypercholesterolemia, coronary atherosclerosis, vulnerable plaques, and myocardial infarction; lipoprotein physiology is more human-like than in mice.	Natural and genetic animal model; LDLR-specific model.	Established comparative-model literature	https://doi.org/10.1590/1414-431X20209557
Nonhuman-primate model	Six genome-edited LDLR-knockout cynomolgus monkeys had severe hyperlipidemia resembling biallelic LDLR-FH, elevated VLDL and LDL, decreased HDL, periocular xanthoma by one year, and strong resistance to lipid-lowering medication.	Primary genome-edited model-organism study; LDLR-specific.	Sato et al., Sep 2023	https://doi.org/10.1038/s41598-023-42763-1

Table: Compact evidence map for LDLR-related familial hypercholesterolemia, distinguishing LDLR-specific findings from evidence generalized from broader FH or HoFH populations. It summarizes identity, genetics, clinical features, diagnosis, interventions, disparities, and experimental models.

1. Disease information

Definition. LDLR-related FH is a congenital, lifelong disorder of LDL clearance caused by reduced quantity or function of the hepatocyte low-density-lipoprotein receptor. One pathogenic allele generally produces heterozygous FH (HeFH); biallelic pathogenic variants produce severe homozygous or compound-heterozygous LDLR-FH. Persistent LDL-cholesterol elevation causes cumulative arterial cholesterol exposure, premature atherosclerotic cardiovascular disease (ASCVD), and, in severe biallelic disease, childhood xanthomas and early coronary or aortic-root disease. LDLR variants account for approximately 90–95% of molecularly defined monogenic FH, although estimates vary by ascertainment. (fularski2024unveilingfamilialhypercholesterolemia—review pages 2-4, kalwick2025acomprehensivereview pages 1-3)

Identifiers and synonyms. Recommended identifiers are MONDO:0007750, “hypercholesterolemia, familial, 1”; OMIM #143890, familial hypercholesterolemia 1; causal gene LDLR, OMIM *606945; and MeSH Familial Hypercholesterolemia. Broader FH maps to MONDO:0005439, while homozygous FH has MONDO:0018328; neither should replace MONDO:0007750 in an LDLR-specific record. Open Targets identifies LDLR as the strongest associated target for MONDO:0007750 (association score 0.877). Common names include LDLR-related familial hypercholesterolemia, familial hypercholesterolemia type 1, autosomal dominant hypercholesterolemia type 1, LDL-receptor deficiency, HeFH due to LDLR, and biallelic/homozygous LDLR-FH. (OpenTargets Search: familial hypercholesterolemia-LDLR)

ICD coding is less gene-specific: ICD-10-CM E78.01 denotes familial hypercholesterolemia, while ICD-11 generally classifies it among genetic disorders of lipoprotein metabolism. ICD codes should therefore be paired with the molecular diagnosis rather than treated as LDLR-specific identifiers.

2. Etiology, risk, protection, and gene–environment interaction

The initiating cause is a germline loss-of-function LDLR variant. De novo variants occur but are uncommon; most cases segregate in families. Null alleles, which produce no functional receptor, generally cause higher LDL-C and greater ASCVD burden than receptor-defective alleles retaining residual function. Copy-number variants may represent roughly 10% of molecular diagnoses in some series, and deep-intronic defects may be missed unless RNA studies or genome sequencing are used. (fularski2024unveilingfamilialhypercholesterolemia—review pages 2-4, fularski2024unveilingfamilialhypercholesterolemia—review pages 4-5)

Genetic severity factors include biallelic LDLR variants, null/null genotypes, high polygenic LDL-C burden, elevated Lp(a), and variants affecting interacting pathways. PCSK9 is a mechanistic modifier: increased PCSK9 activity promotes lysosomal LDLR degradation, whereas PCSK9 loss-of-function preserves receptor abundance and lowers LDL-C and coronary risk. Modifier and polygenic effects explain part—but not all—of variable expressivity. (fularski2024unveilingfamilialhypercholesterolemia—review pages 4-5, taranto2023geneticheterogeneityof pages 1-2)

Environmental/lifestyle factors do not cause LDLR-FH but alter realized ASCVD risk. Smoking, hypertension, diabetes, obesity, physical inactivity, and diets rich in saturated/trans fat add to lifelong LDL burden. In 10,175 case-control and 39,920 cohort participants carrying pathogenic variants in LDLR, APOB, or PCSK9, projected CAD risk by age 75 ranged from 35% with a favorable lifestyle to 66% with an unfavorable lifestyle. This is compelling gene–environment evidence, but it was not reported separately for LDLR. Its abstract conclusion states that “a favorable lifestyle is associated with a lower risk of coronary artery disease in carriers and noncarriers.” DOI: 10.1001/jamanetworkopen.2022.2687.

Protective factors include early diagnosis, lifelong adherence to LDL-lowering treatment, avoidance of tobacco, regular physical activity, healthy weight, and a dietary pattern low in saturated fat and rich in fiber and unsaturated fat. These reduce downstream risk but do not normalize receptor function. PCSK9 loss-of-function and other LDL-lowering alleles are plausible genetic protectors. No infectious, occupational, radiation, or toxin exposure is an established primary cause.

3. Phenotypes

Phenotype	Type, onset, course, frequency	Suggested HPO term
Elevated LDL-C	Laboratory abnormality; present from birth, persistent and usually severe; universal defining feature	HP:0003124 Hypercholesterolemia
Premature atherosclerosis/CAD	Usually subclinical in childhood in HeFH, clinically progressive in adulthood; childhood or adolescence in severe biallelic disease	HP:0002621 Atherosclerosis, HP:0001677 Coronary artery atherosclerosis
Tendon xanthomas	Physical sign; age-dependent, uncommon in adequately treated children, more frequent with severe or longstanding disease	HP:0005039 Xanthomatosis, tendon-xanthoma child term if supported locally
Cutaneous/planar or tuberous xanthomas	Particularly characteristic of severe biallelic disease; may appear in early childhood	HP:0000991 Xanthoma
Corneal arcus	Usually age-dependent; arcus before age 45 is diagnostically informative	HP:0001084 Corneal arcus
Xanthelasma	Variable and nonspecific; more likely with prolonged hypercholesterolemia	HP:0001114 Xanthelasma
Myocardial infarction/angina	Downstream clinical complication; adult-premature in HeFH, potentially childhood in null/null LDLR-FH	HP:0001658 Myocardial infarction, HP:0001681 Angina pectoris
Aortic-root/valvular disease	Especially severe HoFH; progressive supravalvular/aortic-root atherosclerosis and calcific aortic stenosis	HP:0001646 Aortic stenosis
Carotid/peripheral/cerebrovascular disease	Variable downstream manifestations of systemic atherosclerosis	HP:0002635 Cerebral ischemia, HP:0004417 Peripheral arterial stenosis

Reviews consistently describe elevated LDL-C, tendon/skin xanthomas, xanthelasma, corneal arcus, and premature progressive ASCVD. In untreated severe HoFH, coronary disease and aortic stenosis may occur by age 20, death may occur by age 30, and myocardial infarction has occurred before age 10; these figures describe broad HoFH and should not be assigned to every biallelic LDLR genotype. (fularski2024unveilingfamilialhypercholesterolemia—review pages 4-5, abifadel2023geneticandmolecular pages 1-2)

Quality-of-life effects derive less from isolated hypercholesterolemia than from anxiety about inherited risk, polypharmacy, injectable treatment, apheresis schedules, dietary burden, ASCVD disability, and financial/access barriers. Robust LDLR-genotype-specific EQ-5D or SF-36 estimates were not identified; broad HoFH evidence should therefore not be entered as LDLR-specific QoL data.

4. Genetic and molecular information

Gene. LDLR is located at 19p13.2 and encodes the LDL receptor, a cell-surface transmembrane glycoprotein highly expressed by hepatocytes. Recommended identifiers are HGNC:6547, NCBI Gene 3949, and Ensembl ENSG00000130164.

Variant spectrum. Disease-causing variants include missense, nonsense, frameshift, canonical and noncanonical splice variants, promoter defects, in-frame indels, exon-level deletions/duplications, and larger structural rearrangements. Classic functional classes are: (1) absent synthesis; (2) defective ER-to-Golgi transport; (3) impaired APOB-containing LDL binding; (4) impaired clustering/internalization in clathrin-coated pits; and (5) abnormal endosomal dissociation or receptor recycling. Most are loss-of-function; dominant-negative behavior is not the usual mechanism. All are constitutional/germline rather than somatic. (fularski2024unveilingfamilialhypercholesterolemia—review pages 2-4, fularski2024unveilingfamilialhypercholesterolemia—review pages 4-5)

Classification. Variants should be interpreted under ACMG/AMP criteria supplemented by ClinGen FH specifications, segregation, population frequency, LDLR activity assays, cell-surface abundance, LDL binding/uptake, and RNA studies. Pathogenic/likely pathogenic variants establish molecular LDLR-FH; a VUS does not. Clinically encountered pathogenic alleles are usually absent or extremely rare in gnomAD. A single universal allele-frequency cutoff is inappropriate because founder alleles can be locally enriched.

Recent functional genomics. A major post-2024 advance tested approximately 17,000 nearly all-possible LDLR coding variants for cell-surface abundance and LDL uptake. Functional scores correlated with prospective human hyperlipidemia and improved inference when combined with polygenic scores. This 2026 Science study is beyond the requested 2023–2024 priority window but represents the current frontier; DOI 10.1126/science.ady7186. Its abstract states that the maps “provide evidence for interpreting clinical variants.” (tabet2026thefunctionallandscape pages 1-3)

No recurrent aneuploidy, translocation, mitochondrial defect, repeat expansion, or somatic mosaic mechanism characterizes this disease. Large LDLR deletions/duplications are relevant; conventional karyotyping is not. Disease-specific DNA methylation, histone, single-cell, spatial-transcriptomic, proteomic, or metabolomic signatures are not validated diagnostic entities. Altered plasma LDL lipidomics is a direct biochemical consequence, not a unique omics classifier.

5. Environmental information

LDLR-FH is not caused by infection, pollution, radiation, or occupational exposure. Secondary hypercholesterolemia can intensify or mimic the phenotype and should be sought: hypothyroidism, nephrotic syndrome, cholestatic liver disease, uncontrolled diabetes, obesity, pregnancy, and LDL-raising drugs. Diet and exercise usually produce modest LDL changes relative to the inherited defect but materially affect total cardiovascular risk. Smoking is especially avoidable because it acts downstream on endothelial injury and thrombosis. No vaccine or antimicrobial prevention is applicable.

6. Mechanism and pathophysiology

Ordered causal chain

A germline pathogenic LDLR variant leads to absent, reduced, mislocalized, binding-defective, internalization-defective, or recycling-defective LDL receptor.
Reduced functional LDLR at the hepatocyte surface results in impaired receptor-mediated uptake of circulating APOB-100-containing LDL.
Impaired hepatic clearance leads to elevated plasma LDL-C from birth; biallelic/null variants result in the greatest elevation.
Lifelong elevated LDL-C causes increased arterial entry and retention of APOB-containing particles in the subendothelial extracellular matrix.
Retained LDL undergoes oxidative/enzymatic modification and induces endothelial activation, chemokine expression, and monocyte recruitment.
Monocyte-derived macrophages internalize modified LDL through scavenger pathways, forming foam cells and fatty streaks.
Persistent lipid retention and unresolved inflammation lead to smooth-muscle migration/proliferation, extracellular-matrix deposition, necrotic-core formation, and plaque calcification.
Plaque growth results in coronary, carotid, aortic-root, and peripheral stenosis; plaque disruption and thrombosis cause acute coronary syndrome, myocardial infarction, stroke, or sudden death.
Branch: extracellular cholesterol deposition in tendons, skin, and cornea causes xanthomas and corneal arcus.
Branch in severe biallelic disease: extreme LDL exposure at the aortic root/valve leads to supravalvular disease and calcific aortic stenosis. The exact patient-level rate is genotype- and treatment-dependent.

This chain is established through human genetics, receptor biochemistry, pathology, and model systems. LDLR mediates cell-surface endocytosis; PCSK9 binding diverts LDLR toward lysosomal degradation rather than recycling. Accordingly, statins, PCSK9 antibodies, and inclisiran require at least some residual receptor capacity, whereas ANGPTL3 inhibition, MTP inhibition, and apheresis act substantially independently of LDLR. (fularski2024unveilingfamilialhypercholesterolemia—review pages 4-5, bourbon2026thespectrumof pages 8-10)

Suggested annotations include GO:0006897 endocytosis, GO:0006869 lipid transport, GO:0008203 cholesterol metabolic process, GO:0034383 low-density lipoprotein particle clearance, GO:0006954 inflammatory response, and GO:0043277 apoptotic cell clearance. Principal cell types are hepatocyte (CL:0000182), vascular endothelial cell, arterial smooth-muscle cell, circulating monocyte, and macrophage/foam cell. Relevant compartments include plasma membrane (GO:0005886), clathrin-coated pit, endosome, lysosome, endoplasmic reticulum, and Golgi apparatus.

7. Anatomical structures affected

The primary biochemical organ is the liver, particularly hepatocytes that normally clear most circulating LDL. Clinical injury occurs in the arterial system: coronary arteries and myocardium, aortic root and aortic valve, carotid and cerebral arteries, and peripheral arteries. Secondary cholesterol deposits affect Achilles and hand extensor tendons, pressure-bearing skin, eyelids, and peripheral cornea. Suggested terms include UBERON:0002107 liver, UBERON:0000948 heart, UBERON:0001621 coronary artery, UBERON:0001496 ascending aorta, UBERON:0002137 aortic valve, UBERON:0001619 carotid artery, UBERON:0001769 cornea, and UBERON:0000979 Achilles tendon. Findings are generally systemic/bilateral rather than lateralized.

8. Temporal development

The molecular and biochemical disease begins congenitally: LDL-C is elevated from birth and exposure accumulates continuously. HeFH often remains clinically silent through childhood, with subclinical endothelial or carotid changes preceding adult premature ASCVD. Biallelic/null disease may produce xanthomas in early childhood and coronary/aortic disease during childhood or adolescence. The course is chronic and progressive without treatment; spontaneous remission does not occur. Treatment lowers current LDL-C and future risk but does not erase prior cumulative exposure.

The critical intervention window is childhood, before substantial plaque develops. In a 20-year follow-up of 214 children with genetically confirmed FH in 98%, LDL-C fell from 237.3 to 160.7 mg/dL (32%). By age 39, cardiovascular events were 1% in treated offspring versus 26% in affected parents, and cardiovascular mortality was 0% versus 7%. The study concluded that childhood statins “slowed the progression of carotid intima-media thickness and reduced the risk of cardiovascular disease in adulthood” (NEJM, 17 October 2019; DOI 10.1056/NEJMoa1816454; PMID 31618540). This cohort was broad genetic FH, not an exclusively reported LDLR subgroup.

9. Inheritance and population

Inheritance is autosomal dominant with gene-dose/semi-dominant severity: each child of a heterozygous affected person has a 50% risk. Biallelic disease can result from homozygosity, compound heterozygosity, or, rarely, double heterozygosity across FH genes. Penetrance for elevated LDL-C is high but not literally complete; ASCVD penetrance is strongly age-, sex-, treatment-, allele-, Lp(a)-, and lifestyle-dependent. Expressivity is variable. Anticipation is not established. Germline mosaicism is possible in principle but is not a recognized major contributor.

Broad-FH meta-analyses estimate HeFH near 1:250–1:313; one recent review cites approximately 1:280 carriers and HoFH near 3 per million. These are not LDLR-only prevalence estimates. Ethnicity-specific broad-FH estimates range from approximately 1:400 in Asian populations to 1:192 in Black/brown groups, partly reflecting ascertainment and founder effects. (humphries2025geneticdeterminantsof pages 1-2, taranto2023geneticheterogeneityof pages 1-2)

Founder variants produce substantially higher local prevalence in French Canadians, Afrikaners, Lebanese Christian groups, Ashkenazi Jews, Finns, and other isolates. Consanguinity increases the probability of biallelic disease. Both sexes inherit LDLR variants equally, but realized disease and care differ. A 2024 meta-analysis of 25 real-world studies (129,441 participants) found women less likely than men to receive lipid-lowering treatment (OR 0.74, 95% CI 0.66–0.85) or reach LDL-C below 2.5 mmol/L (OR 0.85, 95% CI 0.74–0.97), although fixed-dose trial response did not differ; men had approximately twice the relative risk of major cardiovascular events. This is broad-FH evidence. DOI 10.1093/eurheartj/ehae417, July 2024. (iatan2024sexdifferencesin pages 8-8)

10. Diagnostics

Diagnosis combines: (1) at least two lipid measurements when clinically stable; (2) age-specific untreated LDL-C; (3) personal/family premature ASCVD; (4) tendon xanthomas or premature corneal arcus; (5) exclusion of secondary causes; and (6) molecular testing. Adult suspicion is high around untreated LDL-C ≥190 mg/dL (4.9 mmol/L); pediatric thresholds are lower and must be interpreted with family history. Dutch Lipid Clinic Network categories are definite >8, probable 6–8, and possible 3–5 points. A pathogenic variant confirms molecular FH, but a negative result does not exclude clinical FH. (fularski2024unveilingfamilialhypercholesterolemia—review pages 2-4, humphries2025geneticdeterminantsof pages 1-2)

Recommended genetic workflow: sequence LDLR, APOB, PCSK9, and—according to phenotype/inheritance—LDLRAP1 and phenocopy genes such as ABCG5, ABCG8, LIPA, and CYP27A1; include LDLR deletion/duplication analysis. Test the known familial variant directly in relatives. WES is useful when panels are negative or the phenotype is atypical but may miss CNVs and deep-intronic changes. WGS can identify structural and deep-intronic variants; RNA analysis may demonstrate aberrant splicing. CMA, karyotyping, FISH, mitochondrial sequencing, and repeat-expansion testing are not routine unless another indication exists. (fularski2024unveilingfamilialhypercholesterolemia—review pages 2-4, taranto2023geneticheterogeneityof pages 1-2)

Differential diagnoses include polygenic hypercholesterolemia, APOB-/PCSK9-/APOE-related FH, autosomal-recessive LDLRAP1 disease, sitosterolemia, lysosomal-acid-lipase deficiency, cerebrotendinous xanthomatosis, familial combined hyperlipidemia, and secondary hypercholesterolemia. Lp(a) should be measured because its cholesterol contributes to measured LDL-C and independently raises risk.

Screening. Cascade testing of first-degree relatives is the most efficient LDLR-specific strategy because each has approximately 50% prior risk. Universal or child–parent screening can identify otherwise silent families. Real-world programs summarized in 2023 reported approximately 91% acceptance among Slovenian five-year-olds using opt-out screening and about 60% participation in a West Virginia school program. (gidding2023childhoodscreeningfor pages 4-6)

11. Outcome and prognosis

Untreated prognosis is dominated by premature coronary disease. Older natural-history estimates suggest untreated CHD by age 50 in approximately 50% of men and by age 60 in 30% of women with FH; these historical broad-FH figures predate modern combination therapy. Null alleles, biallelic disease, higher cumulative LDL-C, elevated Lp(a), smoking, diabetes, hypertension, existing ASCVD, and delayed treatment worsen prognosis. (humphries2025geneticdeterminantsof pages 1-2)

Treatment can dramatically normalize the trajectory: the long-term pediatric cohort showed carotid-intima–media-thickness progression similar to unaffected siblings and markedly fewer events than affected parents, although only 20% reached LDL-C below 100 mg/dL. Recovery from established infarction, stenosis, or calcific valve disease is incomplete; the practical goal is lifelong biochemical control and prevention of new events.

12. Treatment

Treatment is genotype-informed but risk-driven. Lifestyle therapy accompanies rather than replaces medication.

High-intensity statin—inhibits HMG-CoA reductase, activates SREBP2, and increases LDLR expression. First-line for HeFH; effect is reduced in receptor-null HoFH. Monitor transaminases and symptoms of myopathy. Suggested NCIT concept: HMG-CoA Reductase Inhibitor Therapy.
Ezetimibe—inhibits intestinal NPC1L1 cholesterol absorption and adds approximately 15–25% LDL-C lowering in typical FH practice. Suggested NCIT: Ezetimibe Therapy.
PCSK9 monoclonal antibodies—evolocumab or alirocumab preserve surface LDLR; response therefore depends on residual receptor function. A 2024 pediatric meta-analysis of nine studies, including three RCTs with 320 children, estimated LDL-C reduction of 37.92% (95% CI 32.78–43.06), apoB reduction of 33.67%, and Lp(a) reduction of 16.94%. Effects were consistent in HeFH but highly variable in HoFH, and agents were generally well tolerated. (xiao2024efficacyandsafety pages 5-8, xiao2024efficacyandsafety pages 1-2)
Inclisiran—GalNAc-siRNA suppressing hepatic PCSK9 synthesis; twice-yearly maintenance dosing improves convenience but remains LDLR-dependent. Pediatric HeFH and HoFH phase 3 programs are active or recently completed; cardiovascular-outcome evidence and genotype-specific pediatric evidence remain less mature than LDL-C evidence.
Bempedoic acid—ATP-citrate-lyase inhibitor used in adults needing additional oral therapy or with statin intolerance; LDL lowering is substantially LDLR-mediated.
Lomitapide—MTP inhibitor that reduces VLDL assembly and LDL production independently of LDLR; reserved for HoFH. Important harms include diarrhea, transaminase elevation, hepatic steatosis, drug interactions, and teratogenic risk; a very-low-fat diet and liver monitoring are required.
Evinacumab—ANGPTL3 monoclonal antibody that lowers LDL-C largely independently of LDLR, making it especially valuable in null/null HoFH. Phase 3 programs include NCT03399786, NCT03409744, and pediatric NCT04233918. Access and intravenous administration remain limitations.
Lipoprotein apheresis—direct extracorporeal removal; one procedure conventionally lowers LDL-C by >60%, but rebound creates a saw-tooth exposure pattern. Weekly/biweekly therapy can regress xanthomas, slow atherosclerosis, and improve survival. In severe childhood HoFH, initiation before approximately age 6–7 is recommended where feasible. (tokgozoglu2021familialhypercholesterolemiaglobal pages 9-10)
Liver transplantation—replaces the principal organ expressing LDLR and can markedly normalize LDL clearance, but operative risk and lifelong immunosuppression restrict it to exceptional refractory biallelic disease.
Pregnancy—preconception counseling is essential. Statins and several systemic agents are usually stopped during pregnancy according to jurisdiction and individual risk; bile-acid sequestrants and apheresis are established non-systemic options. Severe HoFH requires specialist management.

Combination escalation—statin → ezetimibe → PCSK9-directed therapy, followed by LDLR-independent treatment or apheresis in severe biallelic disease—is standard. Pediatric evidence supports early statins; PCSK9 antibodies are added when targets remain unmet. Suggested CHEBI entities include cholesterol (CHEBI:16113) and low-density-lipoprotein cholesterol as the measured analyte; suggested NCIT intervention terms include statin therapy, cholesterol-absorption-inhibitor therapy, monoclonal-antibody therapy, siRNA therapy, therapeutic apheresis, and liver transplantation.

Experimental therapy. Liver-directed LDLR gene replacement, ex-vivo corrected hepatocytes, mRNA delivery, and genome editing remain investigational. Most current in-vivo editing programs reduce PCSK9 or ANGPTL3 rather than repair the diverse LDLR alleles. The 2023 literature identified PCSK9 inhibition, inclisiran, and gene therapy as leading research hotspots. (bourbon2026thespectrumof pages 8-10, taranto2023geneticheterogeneityof pages 1-2)

13. Prevention

Primary genetic prevention is not possible after conception. Reproductive options include genetic counseling, familial-variant prenatal testing, and preimplantation genetic testing, with nondirective counseling. Secondary prevention consists of universal/opportunistic lipid screening, molecular confirmation, cascade testing, and treatment before arterial injury. Tertiary prevention comprises intensive LDL-C lowering, tobacco avoidance, blood-pressure/diabetes management, antiplatelet therapy when otherwise indicated, and surveillance/treatment of coronary and aortic-valve disease.

There is no vaccine. Population priorities are clinician and public awareness, laboratory flagging of very high LDL-C, EHR case-finding, guaranteed cascade-testing pathways, pediatric screening, access to lipid specialists, and equitable availability of combination drugs and apheresis.

14. Other species and natural disease

LDLR orthologues and receptor-mediated LDL clearance are strongly conserved across mammals. Naturally occurring Watanabe heritable hyperlipidemic rabbits (Oryctolagus cuniculus, NCBI Taxon 9986) have LDLR deficiency, LDL-rich hypercholesterolemia, tendon/skin lesions, and spontaneous atherosclerosis. The selectively bred WHHLMI strain develops vulnerable coronary plaques and myocardial infarction and has been important in statin development. Rabbits better reproduce human LDL-dominant lipoprotein physiology than ordinary mice.

Naturally occurring LDLR-related hypercholesterolemia has also been described in some companion-animal families, but breed-specific evidence is too sparse for confident VBO annotations. The condition is inherited, not transmissible or zoonotic.

15. Model organisms

Ldlr−/− mouse (Mus musculus, Taxon 10090) is the standard high-throughput genetic model for LDL clearance, atherogenesis, inflammation, and therapeutic testing. It often requires a Western/cholesterol-rich diet for severe lesions; murine HDL-dominant physiology and limited spontaneous plaque rupture constrain translation.

WHHL/WHHLMI rabbit provides more human-like LDL-rich plasma and spontaneous coronary disease, but breeding, cost, and genetic manipulation are less convenient than in mice.

LDLR-null hamster more closely models human lipoprotein handling and diet-induced coronary atherosclerosis than mice. Zebrafish support developmental and high-throughput lipid studies but incompletely reproduce human coronary disease.

A major recent model advance was six CRISPR-edited LDLR-knockout cynomolgus monkeys (Macaca fascicularis, Taxon 9541). All had confirmed LDLR mutations, markedly elevated cholesterol/triglycerides, elevated VLDL/LDL, reduced HDL, periocular xanthoma by one year, and strong resistance to lipid-lowering medication—closely approximating biallelic LDLR-FH. The authors concluded that the phenotype was “similar to that of homozygous FH patients” (Scientific Reports, September 2023; DOI 10.1038/s41598-023-42763-1). Its limitations are cost, ethics, small sample size, and complete knockout being more severe than many human missense genotypes.

Cellular systems include patient fibroblasts, LDLR-null hepatoma cells, iPSC-derived hepatocyte-like cells, and CRISPR knock-in cells. These quantify LDLR maturation, surface abundance, LDL binding/uptake, endocytosis, and recycling and are especially important for resolving missense/splice VUS.

Knowledge-base cautions and gaps

Enter MONDO:0007750 + a pathogenic/likely pathogenic LDLR variant for the gene-specific disorder; do not equate every clinical FH or HoFH case with LDLR disease.
Frequencies of individual manifestations, allele-specific penetrance, and treatment effects are often unavailable because cohorts combine causal genes.
Disease-specific epigenetic, single-cell, spatial, proteomic, and metabolomic biomarkers are not clinically validated.
The strongest evidence supports LDL-C concentration and cumulative exposure as biomarkers, LDLR genotype/residual activity as severity and treatment-response modifiers, and early sustained LDL lowering as the principal determinant of improved prognosis.

References

(fularski2024unveilingfamilialhypercholesterolemia—review pages 2-4): Piotr Fularski, Joanna Hajdys, Gabriela Majchrowicz, Magdalena Stabrawa, Ewelina Młynarska, Jacek Rysz, and Beata Franczyk. Unveiling familial hypercholesterolemia—review, cardiovascular complications, lipid-lowering treatment and its efficacy. International Journal of Molecular Sciences, 25:1637, Jan 2024. URL: https://doi.org/10.3390/ijms25031637, doi:10.3390/ijms25031637. This article has 30 citations.
(taranto2023geneticheterogeneityof pages 1-2): Maria Donata Di Taranto and Giuliana Fortunato. Genetic heterogeneity of familial hypercholesterolemia: repercussions for molecular diagnosis. Feb 2023. URL: https://doi.org/10.3390/ijms24043224, doi:10.3390/ijms24043224. This article has 54 citations.
(abifadel2023geneticandmolecular pages 1-2): Marianne Abifadel and Catherine Boileau. Genetic and molecular architecture of familial hypercholesterolemia. Oct 2023. URL: https://doi.org/10.1111/joim.13577, doi:10.1111/joim.13577. This article has 189 citations and is from a domain leading peer-reviewed journal.
(xiao2024efficacyandsafety pages 1-2): Guoguang Xiao, Shan Gao, Yongmei Xie, Zhiling Wang, and Min Shu. Efficacy and safety of evolocumab and alirocumab as pcsk9 inhibitors in pediatric patients with familial hypercholesterolemia: a systematic review and meta-analysis. Medicina, 60(10):1646, Oct 2024. URL: https://doi.org/10.3390/medicina60101646, doi:10.3390/medicina60101646. This article has 10 citations.
(OpenTargets Search: familial hypercholesterolemia-LDLR): Open Targets Query (familial hypercholesterolemia-LDLR, 34 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.
(humphries2025geneticdeterminantsof pages 1-2): Steve Eric Humphries and Marta Futema. Genetic determinants of the familial hypercholesterolaemia phenotype. Annals of Human Genetics, 89:293-304, Apr 2025. URL: https://doi.org/10.1111/ahg.12594, doi:10.1111/ahg.12594. This article has 10 citations and is from a peer-reviewed journal.
(kalwick2025acomprehensivereview pages 1-3): Megan Kalwick and Mendel Roth. A comprehensive review of the genetics of dyslipidemias and risk of atherosclerotic cardiovascular disease. Feb 2025. URL: https://doi.org/10.3390/nu17040659, doi:10.3390/nu17040659. This article has 13 citations.
(fularski2024unveilingfamilialhypercholesterolemia—review pages 4-5): Piotr Fularski, Joanna Hajdys, Gabriela Majchrowicz, Magdalena Stabrawa, Ewelina Młynarska, Jacek Rysz, and Beata Franczyk. Unveiling familial hypercholesterolemia—review, cardiovascular complications, lipid-lowering treatment and its efficacy. International Journal of Molecular Sciences, 25:1637, Jan 2024. URL: https://doi.org/10.3390/ijms25031637, doi:10.3390/ijms25031637. This article has 30 citations.
(gidding2023childhoodscreeningfor pages 4-6): Samuel S. Gidding. Childhood screening for familial hypercholesterolemia: jacc review topic of the week. Journal of the American College of Cardiology, 82 15:1558-1563, Oct 2023. URL: https://doi.org/10.1016/j.jacc.2023.07.028, doi:10.1016/j.jacc.2023.07.028. This article has 11 citations and is from a highest quality peer-reviewed journal.
(xiao2024efficacyandsafety pages 5-8): Guoguang Xiao, Shan Gao, Yongmei Xie, Zhiling Wang, and Min Shu. Efficacy and safety of evolocumab and alirocumab as pcsk9 inhibitors in pediatric patients with familial hypercholesterolemia: a systematic review and meta-analysis. Medicina, 60(10):1646, Oct 2024. URL: https://doi.org/10.3390/medicina60101646, doi:10.3390/medicina60101646. This article has 10 citations.
(xiao2024efficacyandsafety pages 4-5): Guoguang Xiao, Shan Gao, Yongmei Xie, Zhiling Wang, and Min Shu. Efficacy and safety of evolocumab and alirocumab as pcsk9 inhibitors in pediatric patients with familial hypercholesterolemia: a systematic review and meta-analysis. Medicina, 60(10):1646, Oct 2024. URL: https://doi.org/10.3390/medicina60101646, doi:10.3390/medicina60101646. This article has 10 citations.
(tokgozoglu2021familialhypercholesterolemiaglobal pages 9-10): Lale Tokgozoglu and Meral Kayikcioglu. Familial hypercholesterolemia: global burden and approaches. Current Cardiology Reports, 23:1-13, Sep 2021. URL: https://doi.org/10.1007/s11886-021-01565-5, doi:10.1007/s11886-021-01565-5. This article has 126 citations and is from a peer-reviewed journal.
(iatan2024sexdifferencesin pages 8-8): Iulia Iatan, Leo E Akioyamen, Isabelle Ruel, Amanda Guerin, Lindsay Hales, Thais Coutinho, Liam R Brunham, and Jacques Genest. Sex differences in treatment of familial hypercholesterolaemia: a meta-analysis. European Heart Journal, 45:3231-3250, Jul 2024. URL: https://doi.org/10.1093/eurheartj/ehae417, doi:10.1093/eurheartj/ehae417. This article has 44 citations and is from a highest quality peer-reviewed journal.
(tabet2026thefunctionallandscape pages 1-3): Daniel R. Tabet, Atina G. Coté, Megan C. Lancaster, Jochen Weile, Ashyad Rayhan, Iosifina Fotiadou, Nishka Kishore, Roujia Li, Da Kuang, Jennifer J. Knapp, Carmela S. Carrero, Olivia Taverniti, Anna Axakova, Jack M. P. Castelli, Mohammad M. Islam, Shahin Sowlati-Hashjin, Aanshi Gandhi, Ranim Maaieh, Michael Garton, Kenneth Matreyek, Douglas M. Fowler, Mafalda Bourbon, Simon G. Pfisterer, Andrew M. Glazer, Brett M. Kroncke, Victoria N. Parikh, Euan A. Ashley, Joshua W. Knowles, Melina Claussnitzer, Elizabeth T. Cirulli, Robert A. Hegele, Dan M. Roden, Calum A. MacRae, and Frederick P. Roth. The functional landscape of coding variation in the familial hypercholesterolemia gene ldlr. Science, 391(6787):eady7186-eady7186, Feb 2026. URL: https://doi.org/10.1126/science.ady7186, doi:10.1126/science.ady7186. This article has 41 citations and is from a highest quality peer-reviewed journal.
(bourbon2026thespectrumof pages 8-10): M. Bourbon, A. C. Alves, J. R. Chora, A. J. Hooper, and M. Abifadel. The spectrum of genetic causes of familial hypercholesterolemia phenotype. Jul 2026. URL: https://doi.org/10.1007/s11883-026-01435-x, doi:10.1007/s11883-026-01435-x. This article has 0 citations and is from a peer-reviewed journal.

Artifacts

Edison artifact artifact-00

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome	Count
References checked	16
Resolved	16
Unresolved (possible confabulation)	0
Unverifiable	0
Quoted claims checked	2
Quoted claims found in source	2
Quoted claims not found in source	0
Quoted claims with nothing to check against	1
References weighed for topical relevance	16
On topic	9
Off topic	0

Quotes that could not be checked

There was no text to compare these against, so they are neither confirmed nor contradicted:

DOI:10.1056/NEJMoa1816454: "slowed the progression of carotid intima-media thickness and reduced the risk of cardiovascular disease in adulthood"
Reference resolved but exposes no abstract or full text to search

All extracted references resolved successfully.

Term Validation

Checked with linkml-term-validator 0.4.5, through the ols: adapter.

Outcome	Count
Terms checked	33
Resolved	32
Unresolved (possible confabulation)	0
Obsolete	0
Unverifiable	1
Terms whose name was checked	1
Terms named correctly	0
Terms named as a different term	1

Terms the report names something else

These identifiers resolve, so nothing about them looks wrong, and the ontology calls them something unrelated to what the report calls them. That usually means the identifier is not the one the sentence needs:

MONDO:0007750 (6 mentions) - the report calls it "if available", "association score 0.877"; MONDO calls it hypercholesterolemia, familial, 1

Terms named inconsistently

The report gives these identifiers more than one name of its own:

MONDO:0007750 - called "if available", "association score 0.877"

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OpenScientist Report

Classifications

Inheritance

Discussions and Knowledge Gaps

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Environmental Factors

Biochemical Markers

Diagnosis

Progression

Prevalence

Differential Diagnoses

Related Datasets

Clinical Trials

Experimental Models

Animal Models

Source YAML

References & Deep Research

References

Deep Research

Disease Characteristics Research Template

Target Disease

Research Objectives

1. Disease Information

2. Etiology

3. Phenotypes

4. Genetic/Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome/Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Citation Requirements

Output Format

LDLR-Related Familial Hypercholesterolemia

Scope and evidence conventions

1. Disease information

2. Etiology, risk, protection, and gene–environment interaction

3. Phenotypes

4. Genetic and molecular information

5. Environmental information

6. Mechanism and pathophysiology

Ordered causal chain

7. Anatomical structures affected

8. Temporal development

9. Inheritance and population

10. Diagnostics

11. Outcome and prognosis

12. Treatment

13. Prevention

14. Other species and natural disease

15. Model organisms

Knowledge-base cautions and gaps

Artifacts

Reference Validation

Quotes that could not be checked

Term Validation

Terms the report names something else

Terms named inconsistently