Autosomal Dominant Osteopetrosis Type I

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Inheritance

1

Autosomal Dominant HP:0000006

Heterozygous LRP5 activating variants segregate as an autosomal dominant trait. Clinical severity varies within families; absence of symptoms is not equivalent to absence of skeletal changes. Historical untyped osteopetrosis cohorts do not provide LRP5-specific penetrance estimates. Recessive loss-of-function LRP5 variants cause the distinct osteoporosis-pseudoglioma syndrome.

Autosomal dominant inheritance

Show evidence (2 references)

PMID:12054167 SUPPORT Human Clinical

"Linkage analysis in two families with ADOI from Danish origin enabled us to assign the disease-causing gene to chromosome 11q12-13."

Dominant segregation in two multigenerational families localised the ADO1 locus to the interval that contains LRP5.

PMID:29208525 SUPPORT Human Clinical

"In both individuals, we detected a novel heterozygous duplication of six basepairs in the LRP5 gene, resulting in an insertion of two amino acids, very likely associated with a gain-of-function."

Affected mother and daughter had a heterozygous in-frame duplication; the report proposes gain of function rather than measuring receptor activity.

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Discussions and Knowledge Gaps

3

Which signals explain reduced resorptive responses in T253I disease, and how far does this mechanism generalize to other LRP5 HBM alleles?

KNOWLEDGE GAP ado1_osteoclast_link_mechanism

Attached to

pathophysiology#Reduced Osteoclast Number and Resorptive Response

Normal tested osteoclast endpoints under supplied RANKL/M-CSF favor environmental dependence but do not prove that the entire intrinsic program is unaffected. The T253I authors proposed altered osteoblastic support without demonstrating a mediator. A later study actually measured circulating RANKL/OPG in 16 affected G171V/N198S carriers, 13 unaffected relatives and unrelated controls; the ratio difference was nonsignificant (p=0.09). This neither proves nor excludes altered local signaling at remodeling surfaces, and does not directly resolve T253I biology. Allele-specific co-culture or in vivo perturbation studies are needed.

Show evidence (1 reference)

PMID:24927689 SUPPORT Human Clinical

"It is also of interest that the RANKL/OPG ratio was higher in the affected individuals than in the other two groups, although this too was not significant."

The ratio was measured, with p=0.09 in Table 1; serum measurements are not a test of local osteoblast–osteoclast mediation.

Does the 19.4% neurological involvement figure reflect the true rate, or ascertainment bias in a literature assembled from case reports?

KNOWLEDGE GAP ado1_neuro_ascertainment_bias

Attached to

pathophysiology#Cranial Foramina Narrowing

The figure comes from pooling published cases across a century of shifting nomenclature, and symptomatic patients are far more likely to be published than the asymptomatic carriers found incidentally on DEXA. The review itself notes that neurological manifestations were previously considered absent, which shows how much the estimate has moved with ascertainment. A population-based or family-based series would be needed to fix the rate.

How does G171V enhance bone accrual despite reduced surface localization in some experimental systems?

KNOWLEDGE GAP ado1_g171v_trafficking

Attached to

pathophysiology#Enhanced Canonical Wnt Signaling in Bone-Forming Cells

Earlier cellular work proposed preserved autocrine signaling with reduced extracellular inhibitor access. The 2026 Wls-deletion experiments did not support preferential rescue by intracellularly retained G171V, but altered resorption and intracellular ligand positioning limit exclusion of every trafficking mechanism. Relative contributions of antagonist resistance, receptor localization and ligand availability remain unresolved.

Show evidence (1 reference)

PMID:42113468 SUPPORT Model Organism

"Wls-deleted mice exhibited a severe low bone mass phenotype whether G171V or A214V was present or not."

Conditional Dmp1-Cre experiments constrain a ligand-independent or intracellular-retention explanation; altered resorption and intracellular ligand localization remain potential confounders.

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Pathophysiology

7

LRP5 Gain-of-Function Variation

Heterozygous LRP5 activating variants cause inherited high bone mass. Many established missense variants cluster in the first extracellular beta-propeller; in-frame insertion alleles also occur. Tested HBM receptor variants have reduced binding or sensitivity to extracellular antagonists. This region participates in a receptor whose ligand binding, trafficking and inhibition are interdependent; it is not simply an isolated non-Wnt-binding brake. The reported cytoplasmic R1414S association has not been functionally shown to use the same mechanism.

LRP5 hgnc:6697

Animal models

Lrp5 p.G171V knock-in mouse Mouse partially recapitulates Carries the orthologous substitution at the endogenous locus, and reproduces the defining property of the human allele, resistance to sclerostin.

Lrp5 p.A214V knock-in mouse Mouse partially recapitulates Reproduces sclerostin resistance but remains more sensitive than G171V to DKK1. Under DKK1 challenge, A214V whole-body aBMD fell by approximately 11–14%, with site-specific effects.

Downstream

Enhanced Canonical Wnt Signaling in Bone-Forming Cells Reduced antagonist sensitivity can enhance Wnt signaling. The magnitude and inhibitor specificity depend on the allele.

Show evidence (3 references)

PMID:12579474 SUPPORT Human Clinical

"Like the previously reported mutation (G171V) that causes the high-bone-mass phenotype, all mutations are located in the aminoterminal part of the gene, before the first epidermal growth factor-like domain."

First-propeller clustering in the alleles studied in 2003; this is not an exhaustive statement about all subsequently reported variants.

PMID:29208525 SUPPORT Human Clinical

"In both individuals, we detected a novel heterozygous duplication of six basepairs in the LRP5 gene, resulting in an insertion of two amino acids, very likely associated with a gain-of-function."

Affected mother and daughter had a heterozygous in-frame duplication; the report proposes gain of function rather than measuring receptor activity.

PMID:17052975 SUPPORT In Vitro

"Here we show that LRP5 HBM mutant proteins exhibit reduced binding to a secreted bone-specific LRP5 antagonist, SOST, and consequently are more refractory to inhibition by SOST."

Receptor assays support reduced antagonist sensitivity, not complete loss of all feedback or ligand-independent activation.

Enhanced Canonical Wnt Signaling in Bone-Forming Cells

LRP5 HBM variants can enhance canonical Wnt signaling by reducing inhibition by sclerostin and, variably, DKK1. This does not imply complete loss of feedback or constitutive ligand-independent signaling. Homozygous G171V and A214V mice resisted many skeletal effects of SOST overexpression, but some architectural responses remained; A214V was more responsive to DKK1 than G171V. In conditional mice, neither allele rescued severe osteopenia caused by Wls deletion in late osteoblasts/osteocytes, limiting a proposed autonomous intracellular-signaling explanation.

osteoblast CL:0000062

canonical Wnt signaling pathway GO:0060070 ↑ INCREASED

Animal models

Conditional Lrp5 HBM with Wls deletion in late osteoblasts and osteocytes Mouse partially recapitulates Perturbation tests the dependence of HBM behavior on the ligand-secretion environment.

Downstream

Increased Osteoblastic Bone Formation Enhanced Wnt signaling promotes bone accrual through osteoblast-lineage activity, with effects varying by surface, genotype and age.

Reduced Osteoclast Number and Resorptive Response Altered osteoblast-lineage support is one proposed explanation for the T253I in vivo/culture discrepancy. RANKL/OPG or other mediators have not been shown to carry this causal effect in patients.

Show evidence (3 references)

PMID:18328982 SUPPORT REVIEW SYNTHESIS Other

"Other less common recessive or dominant sclerosing disorders, such as endosteal hyperostosis, sclerostosis, van Buchen disease and high bone mass syndrome, are due to mutations in two genes (LRP5 and SOST) of the Wnt pathway that induce increased osteoblast activity."

Attributes the increased osteoblast activity in this disease group to Wnt pathway gene mutations.

PMID:17052975 SUPPORT In Vitro

"Here we show that LRP5 HBM mutant proteins exhibit reduced binding to a secreted bone-specific LRP5 antagonist, SOST, and consequently are more refractory to inhibition by SOST."

Receptor assays support reduced antagonist sensitivity, not complete loss of all feedback or ligand-independent activation.

PMID:42113468 SUPPORT Model Organism

"Wls-deleted mice exhibited a severe low bone mass phenotype whether G171V or A214V was present or not."

Conditional Dmp1-Cre experiments constrain a ligand-independent or intracellular-retention explanation; altered resorption and intracellular ligand localization remain potential confounders.

Increased Osteoblastic Bone Formation

Increased bone-forming activity contributes to high bone mass, with genotype-, surface- and age-dependent effects. Prior T253I histomorphometry reported increased mineralizing surface, while the later T3 study found normal baseline formation markers and a normal stimulated formation response. Dynamic labeling in HBM knock-in mice demonstrates increased formation on selected surfaces. A normal T3 response alone is not evidence of elevated formation, and mature patient bone does not necessarily continue accumulating rapidly throughout adulthood.

osteoblast CL:0000062

bone mineralization GO:0030282 ↑ INCREASED

Downstream

Excess Skeletal Bone Accrual

Show evidence (2 references)

PMID:16251418 SUPPORT BACKGROUND Human Clinical

"Patients with a T253I mutation in LRP5 have a high bone mass phenotype, characterized by increased mineralizing surface index but abnormally low numbers of small osteoclasts."

The T253I paper summarizes prior patient histomorphometry in its introduction; this is not a new measurement of increased formation in its T3 experiment.

PMID:42113468 SUPPORT Model Organism

"On the endocortical surface, mineralizing surface and bone formation rates were increased in all 3 HBM genotypes compared to controls, at both time points, with the exception of BFR/BS in heterozygous G171V/A214V mice at the later time point."

Global homozygous or compound-mutant mice; dynamic histomorphometry is surface- and time-dependent and differs from the heterozygous human genotype.

Reduced Osteoclast Number and Resorptive Response

Mechanism confidence: Provisional

In studied T253I patients, historical histology showed fewer small osteoclasts and an in vivo T3 challenge produced an attenuated resorption response despite a normal formation response. Patient CD14-derived osteoclasts supplied with RANKL and M-CSF were normal for the tested culture endpoints. These results favor a context-dependent defect but do not exclude every cell-intrinsic contribution. The clinical response and osteoclast-number phenotype should not be generalized to every LRP5 HBM allele.

osteoclast CL:0000092

bone resorption GO:0045453 ↓ DECREASED

Downstream

Excess Skeletal Bone Accrual Reduced resorptive responses may contribute to high bone mass in the studied T253I context; their mediator and contribution relative to formation remain unresolved.

Show evidence (3 references)

PMID:16251418 SUPPORT In Vitro

"We found normal osteoclastogenesis, expression of osteoclast markers, morphology, and localization of proteins involved in bone resorption, such as ClC-7 and cathepsin K."

Patient monocytes differentiated under supplied RANKL/M-CSF showed normal tested markers and morphology. This culture environment bypasses some physiological support signals.

PMID:16251418 SUPPORT In Vitro

"These data demonstrate that ADOI osteoclasts are normal with respect to all aspects investigated in vitro."

Negative results are bounded to the endpoints and culture conditions tested; they do not prove that all osteoclast-intrinsic pathways are unaffected.

PMID:16251418 SUPPORT Human Clinical

"We found attenuated resorptive response to T3 stimulation, despite a normal bone formation response, in alignment with the reduced number of osteoclasts in vivo."

T253I clinical stimulation study; the displayed resorption comparison included six patients and nine controls, rather than every enrolled participant.

Excess Skeletal Bone Accrual

High bone mass affects the skull and long-bone cortices, with variable trabecular and cortical remodeling. Human skull tissue from an insertion-allele carrier showed lamellar organization and normal mineralization with region-specific remodeling. Fractures can occur, but excess fracture susceptibility and marrow failure are not characteristic of LRP5 HBM.

Downstream

Cranial Foramina Narrowing Hyperostotic cranial bone can encroach on nerve passages.

Increased bone mineral density

Generalized osteosclerosis The radiographic phenotype records diffuse excess bone density.

Craniofacial hyperostosis Excess bone accrual can thicken cranial and facial bones.

Torus palatinus Localized palatal bone overgrowth produces a torus.

Mandibular enlargement Craniofacial bone accrual can enlarge the mandible.

Bone pain Pain accompanies skeletal overgrowth in some patients; the specific nociceptive mediator is unresolved.

Reduced Intracranial Space Skull thickening can reduce available intracranial space.

Spinal canal stenosis Excess vertebral bone may narrow the spinal canal in reported cases.

Show evidence (2 references)

PMID:12054167 SUPPORT Human Clinical

"Within the autosomal dominant form of osteopetrosis, the radiological type I (ADOI) is characterized by a generalized osteosclerosis, most pronounced at the cranial vault."

Defines the radiological hallmark and its cranial predominance, which is what drives the neurological consequences downstream.

PMID:29208525 SUPPORT Human Clinical

"Our findings indicate normal morphology of osteoclasts and osteoblasts as well as normal mineralization in skull bone in LRP5-HBM."

Histology and mineralization measurements from surgically removed occipital bone in one insertion-allele carrier; not proof of identical architecture at all sites or in all patients.

Cranial Foramina Narrowing

Hyperostotic bone can narrow cranial nerve passages and cause hearing loss, facial palsy or trigeminal symptoms. The timing is variable: congenital hearing impairment was reported in an insertion-allele carrier. Anosmia has been reported, but its exact anatomic mediator was not demonstrated in that case.

Downstream

Hearing impairment Auditory canal narrowing can contribute to hearing impairment.

Anosmia Olfactory dysfunction may relate to cranial hyperostosis; cribriform compression was not directly established.

Facial palsy Facial nerve compression can produce palsy.

Trigeminal neuralgia Nerve compression may contribute to neuralgia; bony crowding and neurovascular conflict can coexist.

Visual impairment Optic nerve compression is reported in the historical clinical literature.

Show evidence (2 references)

PMID:37659026 SUPPORT REVIEW SYNTHESIS Other

"In summary, neurological involvement may occur because of nerve tissue compression by hyperostotic bone, cerebellar disturbances due to a reduction in size of the posterior cranial fossa or tonsillar herniation, and chronic intracranial hypertension"

Distinguishes direct nerve compression from reduced posterior-fossa space and pressure-related complications.

PMID:37659026 SUPPORT Human Clinical

"At age 35, external hearing aids were placed due to complete, bilateral, and mixed hearing loss caused by the narrowing of internal and external acoustic meati."

Index A242T case with anatomically described auditory canal narrowing.

Reduced Intracranial Space

Cranial hyperostosis may reduce posterior fossa capacity or intracranial compliance, with tonsillar herniation and raised pressure. This route is distinct from direct compression of individual nerves in foramina.

Downstream

Increased intracranial pressure Reported pressure/crowding-related neurologic complication.

Papilledema Reported pressure/crowding-related neurologic complication.

Chiari malformation Reported pressure/crowding-related neurologic complication.

Headache Reported pressure/crowding-related neurologic complication.

Show evidence (1 reference)

PMID:37659026 SUPPORT REVIEW SYNTHESIS Other

"In summary, neurological involvement may occur because of nerve tissue compression by hyperostotic bone, cerebellar disturbances due to a reduction in size of the posterior cranial fossa or tonsillar herniation, and chronic intracranial hypertension"

Distinguishes direct nerve compression from reduced posterior-fossa space and pressure-related complications.

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Pathograph

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Phenotypes

18

Ear 1

Hearing impairment OCCASIONAL HP:0000365

Show evidence (3 references)

PMID:12054167 SUPPORT Human Clinical

"The patients are often asymptomatic but some suffer from pain and hearing loss."

Reports hearing loss among symptoms; the 9/54 frequency estimate comes from the later literature synthesis.

PMID:37659026 SUPPORT Human Clinical

"A 44-year-old Caucasian woman with torus palatinus complained of headache, hypo-/anosmia, and complete mixed deafness."

Documents mixed deafness in a genetically confirmed case.

PMID:36971833 SUPPORT REVIEW SYNTHESIS Other

"The clinical phenotypes mainly included: mandibular enlargement (51/57), prominence of torus palatinus (44/62), bone pain (21/59), headache (12/51), hearing loss (9/54), facial nerve palsy (7/56), and vision loss (2/53)."

Literature synthesis uses a different denominator for each recorded feature; these are selected published cases, not prospective carrier risks.

Eye 2

Papilledema HP:0001085

Show evidence (1 reference)

PMID:37659026 SUPPORT REVIEW SYNTHESIS Other

"Cranial nerve deficits and/or other neurologic complications (e.g., intracranial hypertension, headache, spinal canal stenosis, sensitive neuropathy, papilledema, type I Chiari malformation, nausea and/or vomiting, migraine, and cerebellar tonsillar herniation) were present in 30 patients."

Listed among the neurologic complications recorded across the 155-patient review. No per-manifestation frequency is given, only the 19.4% aggregate for neurological involvement, so no frequency is asserted here.

Visual impairment VERY_RARE HP:0000505

Show evidence (1 reference)

PMID:36971833 SUPPORT REVIEW SYNTHESIS Other

"The clinical phenotypes mainly included: mandibular enlargement (51/57), prominence of torus palatinus (44/62), bone pain (21/59), headache (12/51), hearing loss (9/54), facial nerve palsy (7/56), and vision loss (2/53)."

Literature synthesis uses a different denominator for each recorded feature; these are selected published cases, not prospective carrier risks.

Head and Neck 5

Craniofacial hyperostosis HP:0004493

Show evidence (2 references)

PMID:37659026 SUPPORT REVIEW SYNTHESIS Other

"Facial changes and torus palatinus were observed in 61% and 41% of cases, respectively."

Facial changes were reported in 93/153 assessable historical cases, without a standardized hyperostosis endpoint.

PMID:29208525 SUPPORT Human Clinical

"increased calvarial thickness, and thickened cortices of the long bones but no history of fractures"

Cranial and long-bone thickening in two molecularly characterized family members.

Torus palatinus HP:0100789

Show evidence (2 references)

PMID:37659026 SUPPORT REVIEW SYNTHESIS Other

"Facial changes and torus palatinus were observed in 61% and 41% of cases, respectively."

Tori were documented in 58 of 140 cases with ascertainable status, not 41% of all 155 cases.

PMID:36971833 SUPPORT REVIEW SYNTHESIS Other

"The clinical phenotypes mainly included: mandibular enlargement (51/57), prominence of torus palatinus (44/62), bone pain (21/59), headache (12/51), hearing loss (9/54), facial nerve palsy (7/56), and vision loss (2/53)."

Literature synthesis uses a different denominator for each recorded feature; these are selected published cases, not prospective carrier risks.

Anosmia HP:0000458

Show evidence (1 reference)

PMID:37659026 SUPPORT Human Clinical

"A 44-year-old Caucasian woman with torus palatinus complained of headache, hypo-/anosmia, and complete mixed deafness."

Documents hyposmia/anosmia in a genetically confirmed LRP5 case.

Facial palsy OCCASIONAL HP:0010628

Show evidence (1 reference)

PMID:36971833 SUPPORT REVIEW SYNTHESIS Other

"The clinical phenotypes mainly included: mandibular enlargement (51/57), prominence of torus palatinus (44/62), bone pain (21/59), headache (12/51), hearing loss (9/54), facial nerve palsy (7/56), and vision loss (2/53)."

Literature synthesis uses a different denominator for each recorded feature; these are selected published cases, not prospective carrier risks.

Mandibular enlargement VERY_FREQUENT Increased size of the mandible HP:0040309

Show evidence (1 reference)

PMID:36971833 SUPPORT REVIEW SYNTHESIS Other

"The clinical phenotypes mainly included: mandibular enlargement (51/57), prominence of torus palatinus (44/62), bone pain (21/59), headache (12/51), hearing loss (9/54), facial nerve palsy (7/56), and vision loss (2/53)."

Literature synthesis uses a different denominator for each recorded feature; these are selected published cases, not prospective carrier risks.

Metabolism 1

Elevated circulating alkaline phosphatase concentration VERY_RARE HP:0003155

Show evidence (1 reference)

PMID:37659026 SUPPORT REVIEW SYNTHESIS Other

"Elevated serum ALP levels are present in a minority of patients (3.7%), and facial changes and torus palatinus are not consistent findings, with a prevalence of approximately 61% and 41%, respectively."

Five of 136 cases with reported ALP status had elevated values; not five of all 155 cases.

Musculoskeletal 4

Generalized osteosclerosis HP:0005789

Show evidence (1 reference)

PMID:12054167 SUPPORT Human Clinical

"Within the autosomal dominant form of osteopetrosis, the radiological type I (ADOI) is characterized by a generalized osteosclerosis, most pronounced at the cranial vault."

The defining radiological criterion for ADO1.

Increased bone mineral density VERY_FREQUENT HP:0011001

Show evidence (2 references)

PMID:37659026 SUPPORT Human Clinical

"Dual-energy X-ray absorptiometry (DEXA) scan revealed elevated bone mass."

Densitometric confirmation in a genetically confirmed LRP5 case.

PMID:36971833 SUPPORT REVIEW SYNTHESIS Other

"the proportion of patients with elevated BMD at lumbar spine and hip were 40/43, 26/31, respectively"

Measurement-specific denominators in a literature synthesis; reports overlap with other reviews and should not be pooled as independent samples.

Absence of increased fracture rate EXCLUDED Increased susceptibility to fractures HP:0002659

Show evidence (1 reference)

PMID:12054167 SUPPORT Human Clinical

"ADOI is the only type of osteopetrosis not associated with an increased fracture rate."

The negative annotation concerns excess susceptibility, not the occurrence of any fracture.

Spinal canal stenosis HP:0003416

Show evidence (1 reference)

PMID:37659026 SUPPORT REVIEW SYNTHESIS Other

"Two related Japanese patients presented with chronic occipital headache and spinal canal stenosis causing pain and paresthesias in the upper limb"

Historical literature synthesis; no genotype-specific frequency estimate.

Nervous System 3

Headache OCCASIONAL HP:0002315

Show evidence (2 references)

PMID:37659026 SUPPORT Human Clinical

"A 44-year-old Caucasian woman with torus palatinus complained of headache, hypo-/anosmia, and complete mixed deafness."

Documents headache as a presenting neurological complaint.

PMID:36971833 SUPPORT REVIEW SYNTHESIS Other

"The clinical phenotypes mainly included: mandibular enlargement (51/57), prominence of torus palatinus (44/62), bone pain (21/59), headache (12/51), hearing loss (9/54), facial nerve palsy (7/56), and vision loss (2/53)."

Literature synthesis uses a different denominator for each recorded feature; these are selected published cases, not prospective carrier risks.

Increased intracranial pressure HP:0002516

Show evidence (1 reference)

PMID:37659026 SUPPORT REVIEW SYNTHESIS Other

"Cranial nerve deficits and/or other neurologic complications (e.g., intracranial hypertension, headache, spinal canal stenosis, sensitive neuropathy, papilledema, type I Chiari malformation, nausea and/or vomiting, migraine, and cerebellar tonsillar herniation) were present in 30 patients."

Listed among the neurologic complications recorded across the 155-patient review. No per-manifestation frequency is given, only the 19.4% aggregate for neurological involvement, so no frequency is asserted here.

Chiari malformation HP:0002308

Show evidence (1 reference)

PMID:37659026 SUPPORT REVIEW SYNTHESIS Other

"Cranial nerve deficits and/or other neurologic complications (e.g., intracranial hypertension, headache, spinal canal stenosis, sensitive neuropathy, papilledema, type I Chiari malformation, nausea and/or vomiting, migraine, and cerebellar tonsillar herniation) were present in 30 patients."

Listed among the neurologic complications recorded across the 155-patient review. No per-manifestation frequency is given, only the 19.4% aggregate for neurological involvement, so no frequency is asserted here.

Constitutional 2

Bone pain FREQUENT HP:0002653

Show evidence (2 references)

PMID:12054167 SUPPORT Human Clinical

"The patients are often asymptomatic but some suffer from pain and hearing loss."

Reports pain in symptomatic patients, without quantifying a frequency band.

PMID:36971833 SUPPORT REVIEW SYNTHESIS Other

"The clinical phenotypes mainly included: mandibular enlargement (51/57), prominence of torus palatinus (44/62), bone pain (21/59), headache (12/51), hearing loss (9/54), facial nerve palsy (7/56), and vision loss (2/53)."

Literature synthesis uses a different denominator for each recorded feature; these are selected published cases, not prospective carrier risks.

Trigeminal neuralgia HP:0100661

Show evidence (1 reference)

PMID:37659026 SUPPORT Human Clinical

"Our patient reported complete and bilateral hearing loss, trigeminal neuralgia, transient facial palsy, and hypo-/anosmia"

Clinical A242T case; no phenotype-specific frequency estimate.

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Genetic Associations

1

LRP5

Gene: LRP5 hgnc:6697 relationship_type: CAUSATIVE variant_origin: GERMLINE

Show evidence (6 references)

PMID:12579474 SUPPORT Human Clinical

"Thirteen of these were confirmed as polymorphisms, but six novel missense mutations (D111Y, G171R, A214T, A214V, A242T, and T253I) are most likely disease causing."

Identifies the LRP5 missense alleles found in patients ascertained with increased bone density including osteopetrosis type I.

PMID:12579474 SUPPORT Human Clinical

"We performed mutation analysis of the LRP5 gene in 10 families or isolated patients with different conditions with an increased bone density, including endosteal hyperostosis, Van Buchem disease, autosomal dominant osteosclerosis, and osteopetrosis type I."

Establishes that osteopetrosis type I was among the high-bone-density conditions in which LRP5 was screened, linking the gene to this entry's disease.

PMID:37659026 SUPPORT REVIEW SYNTHESIS Other

"LRP5 high bone mass (HBM) is an autosomal dominant endosteal hyperostosis caused by mutations of the low-density lipoprotein receptor-related protein 5 (LRP5) gene."

Confirms LRP5 as the causative gene under the disorder's modern designation.

+ 3 more references

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Medical Actions

5

Clinical surveillance

Action: Supportive Care NCIT:C15747

Management is individualized to skeletal and neurologic symptoms. Hearing, cranial nerve deficits and signs of intracranial hypertension warrant clinical assessment. The cited case literature does not establish a standard surveillance interval or a disease-modifying treatment.

Show evidence (1 reference)

PMID:37659026 SUPPORT REVIEW SYNTHESIS Other

"In summary, neurological involvement may occur because of nerve tissue compression by hyperostotic bone, cerebellar disturbances due to a reduction in size of the posterior cranial fossa or tonsillar herniation, and chronic intracranial hypertension"

Distinguishes direct nerve compression from reduced posterior-fossa space and pressure-related complications.

Hearing rehabilitation

Action: Hearing rehabilitation Ontology label: Rehabilitation NCIT:C15315

Platform: Device

External hearing aids were used for mixed deafness in the A242T index case. This observation supports individualized hearing rehabilitation without establishing comparative efficacy.

Show evidence (1 reference)

PMID:37659026 SUPPORT Human Clinical

"At age 35, external hearing aids were placed due to complete, bilateral, and mixed hearing loss caused by the narrowing of internal and external acoustic meati."

Index A242T case with anatomically described auditory canal narrowing.

Specialist surgical decompression

Action: Specialist surgical decompression Ontology label: Surgical Procedure NCIT:C15329

Platform: Surgery

Occipital decompression has been reported in an LRP5 insertion-allele carrier with foramen magnum stenosis. A separate clinically diagnosed, genetically untested ADO1 case had temporary relief after posterior fossa decompression and prolonged relief after microvascular decompression for recurrent trigeminal neuralgia. These selected cases support evaluation of documented compressive complications, not routine prophylactic surgery or disease modification.

Show evidence (2 references)

PMID:29208525 SUPPORT Human Clinical

"When the daughter had part of the occipital bone surgically removed, the bone sample was used for the visualization of bone lamellar structure and bone cells as well as the measurement of bone mineralization density distribution (BMDD)."

Confirms surgery in a genetically characterized case without supplying a controlled efficacy estimate.

PMID:41431003 SUPPORT Human Clinical

"Throughout more than 5 years of follow-up, she remained entirely pain-free, without recurrence, and had discontinued all medications."

Outcome after second-stage microvascular decompression in one clinically diagnosed ADO1 case; genetic testing was not performed.

Mandibular reduction surgery

Action: Mandibular reduction surgery Ontology label: Surgical Procedure NCIT:C15329

Platform: Surgery

A young woman diagnosed with Worth syndrome underwent mandibular reduction using cutting guides. This is a single reported surgical outcome for mandibular enlargement; the available abstract does not establish her genotype or comparative efficacy.

Show evidence (1 reference)

PMID:36907844 SUPPORT Human Clinical

"The authors report the preoperative considerations in a young female with Worth syndrome, operative planning, and successful mandibular reduction using cutting guides."

Primary surgical case using the historical Worth designation; limited to the available abstract.

Cochlear implantation

Action: cochlear device implantation Ontology label: Surgical Procedure NCIT:C15329

Platform: Device

A molecularly characterized insertion-allele carrier with congenital hearing impairment underwent cochlear implantation. The available abstract does not quantify hearing benefit.

Show evidence (1 reference)

PMID:29208525 SUPPORT Human Clinical

"the daughter suffered from congenital hearing impairment resulting in cochlear implantation, recurrent facial palsy, and migraine"

Primary report of hearing rehabilitation in a molecularly characterized family.

🔬

Diagnosis

3

Skeletal survey and bone densitometry

Radiographs characterize skull-vault and long-bone cortical thickening, while DXA quantifies density. The classic type I pattern differs from the skull-base, sandwich-vertebra and bone-within-bone pattern of type II, but clinical overlap and LRP6 phenocopies make molecular assessment useful. Normal DXA does not automatically exclude a reported cortical-overgrowth phenotype.

Show evidence (1 reference)

PMID:37659026 SUPPORT Human Clinical

"Dual-energy X-ray absorptiometry (DEXA) scan revealed elevated bone mass."

DEXA is the densitometric confirmation step used in the reported workup.

LRP5 sequencing

LRP5 analysis in the context of imaging and family history distinguishes molecularly supported LRP5 high bone mass from other sclerosing dysplasias. Testing should accommodate sequence variants and small in-frame changes rather than assuming every causal variant is a first-propeller missense substitution. A reported cytoplasmic association remains functionally unconfirmed.

Show evidence (2 references)

PMID:37659026 SUPPORT REVIEW SYNTHESIS Other

"Genetic analysis and appropriate denomination of LRP5 HBM are fundamental for diagnosis and to mitigate the confusion that has long characterized this disease."

States that molecular analysis is central to establishing this diagnosis.

PMID:29208525 SUPPORT Human Clinical

"In both individuals, we detected a novel heterozygous duplication of six basepairs in the LRP5 gene, resulting in an insertion of two amino acids, very likely associated with a gain-of-function."

Affected mother and daughter had a heterozygous in-frame duplication; the report proposes gain of function rather than measuring receptor activity.

Bone turnover and circulating Wnt-inhibitor measurements

Normal turnover markers do not exclude high bone mass. In 16 G171V/N198S carriers, 13 unaffected relatives and 24 unrelated controls, mean affected Z-score was 6.4 but CTX and P1NP did not differ significantly across groups. Sclerostin and DKK1 did not distinguish carriers from relatives. SFRP-4 was higher in both affected and unaffected relatives than unrelated controls, so it did not discriminate mutation status within those kindreds. These measurements are not validated confirmatory tests. A prior T253I study had different biomarker findings, limiting generalization across alleles.

Show evidence (4 references)

PMID:24927689 SUPPORT Human Clinical

"There were no differences in CTX or P1NP values among the three groups."

Normal-group comparisons despite marked high bone mass; lack of significance is not universal equivalence.

PMID:24927689 SUPPORT Human Clinical

"There was no group effect for sclerostin when analyzed by one-way ANOVA"

Direct measurement in the G171V/N198S kindred comparison.

PMID:24927689 SUPPORT Human Clinical

"there was an overall group effect by one-way ANOVA. When an ANCOVA analysis was conducted for Dkk-1, controlling for age did not affect the results in any pair-wise comparisons among the three groups, all of which remained nonsignificant."

DKK1 did not show significant pairwise differences despite a borderline overall group effect.

+ 1 more reference

📈

Progression

1

Variable onset and adult course

Clinical timing varies: congenital hearing impairment is documented in an insertion-allele carrier, while adult bone mass need not increase continuously. The 8–76-year symptom-onset range in the historical Funen survey is not a molecularly defined LRP5 estimate and is not transferred here. Cross-sectional age associations do not establish individual longitudinal BMD trajectories.

Show evidence (2 references)

PMID:29208525 SUPPORT Human Clinical

"the daughter suffered from congenital hearing impairment resulting in cochlear implantation, recurrent facial palsy, and migraine"

Congenital hearing impairment documents early onset in a molecularly characterized insertion-allele carrier.

PMID:24927689 SUPPORT BACKGROUND Human Clinical

"individuals with HBM mutations in LRP5 do not generally show progressive increases in bone mass as adults."

Clinical context cited in the biomarker paper discussion; not a longitudinal measurement from its cross-sectional study.

📊

Prevalence

1

Worldwide, cases reported in the literature

Cases In Literature Rare

A 2023 historical review assembled 155 clinically described cases, of whom 64 had genetic testing. This is a literature count across changing terminology and ascertainment, not a population prevalence estimate or a genetically confirmed carrier cohort.

Show evidence (2 references)

PMID:37659026 SUPPORT REVIEW SYNTHESIS Other

"Including the present case, 155 patients have been reported to date."

Historical literature count, including molecularly untested cases; no population denominator.

PMID:37659026 SUPPORT REVIEW SYNTHESIS Other

"The available literature shows that this rare bone disorder is characterized by radiographically evident and generalized endosteal hyperostosis"

The review explicitly calls the disorder rare. The literature count does not independently establish an ultra-rare population threshold.

🔀

Differential Diagnoses

4

Conditions with similar clinical presentations that must be differentiated from Autosomal Dominant Osteopetrosis Type I:

Autosomal dominant osteopetrosis type II (Albers-Schonberg disease)

Overlapping Features CLCN7-related dominant osteopetrosis has a resorption defect, often with sandwich vertebrae, bone-within-bone changes and increased fracture susceptibility. Clinical variability means that absence of fractures alone does not exclude it.

Show evidence (1 reference)

PMID:12054167 SUPPORT Human Clinical

"ADOI is the only type of osteopetrosis not associated with an increased fracture rate."

The fracture-rate contrast is the stated discriminator between ADO1 and the other osteopetroses.

LRP6 high bone mass

Overlapping Features LRP6-related high bone mass can resemble LRP5 disease clinically. A negative LRP5 result prompts consideration of LRP6 and other sclerosing dysplasias; it does not establish an LRP6 diagnosis.

Show evidence (2 references)

PMID:37659026 SUPPORT REVIEW SYNTHESIS Other

"the detection of pathogenic mutations in the low-density lipoprotein receptor-related protein 6 (LRP6) gene in some patients with autosomal dominant HBM phenotype led to the description of a clinically identical disorder in 2019, called LRP6 HBM"

Establishes LRP6 HBM as a separate gene producing a clinically identical high-bone-mass disorder.

PMID:37659026 SUPPORT REVIEW SYNTHESIS Other

"when comparing the affected individuals with patients carrying LRP5 mutations, no feature was found to differentiate LRP6 HBM from LRP5 HBM"

States directly that no clinical feature separates the two, which is why this differential is resolvable only by sequencing.

Sclerosteosis and van Buchem disease

Overlapping Features Sclerosteosis and van Buchem disease reduce sclerostin activity through SOST coding or regulatory defects and can cause marked skeletal overgrowth. They involve the same antagonist–receptor pathway as LRP5 high bone mass, with different inheritance and molecular causes.

Show evidence (1 reference)

PMID:18328982 SUPPORT REVIEW SYNTHESIS Other

"Other less common recessive or dominant sclerosing disorders, such as endosteal hyperostosis, sclerostosis, van Buchen disease and high bone mass syndrome, are due to mutations in two genes (LRP5 and SOST) of the Wnt pathway that induce increased osteoblast activity."

Groups the SOST and LRP5 disorders as the same Wnt-axis differential.

Osteoporosis-pseudoglioma syndrome

Overlapping Features Recessive loss-of-function LRP5 disease causes osteoporosis-pseudoglioma syndrome, with low bone mass and ocular disease. It is an allelic contrast rather than a high-bone-mass clinical phenocopy.

Show evidence (1 reference)

PMID:12579474 SUPPORT Human Clinical

"The LDL receptor-related protein 5 (LRP5) gene has been shown to be involved in both osteoporosis-pseudoglioma syndrome and the high-bone-mass phenotype and turned out to be an important regulator of peak bone mass in vertebrates."

Establishes the allelic relationship between the low- and high-bone-mass LRP5 disorders.

🐁

Animal Models

3

Lrp5 p.G171V knock-in mouse

The 2015 inhibitor-challenge study used homozygous G171V knock-in mice. Endogenous-locus expression preserves regulatory context but differs from the usual heterozygous human genotype. Skeletal responses depend on inhibitor, site and sex.

Species

Mouse

Genotype

Homozygous Lrp5 p.G171V knock-in at the endogenous locus, crossed with SOST- or Dkk1-overexpressing transgenes

Publication

PMID:25808845

Pathograph links

LRP5 Gain-of-Function Variation partially recapitulates fidelity: moderate observes: organism Carries the orthologous substitution at the endogenous locus, and reproduces the defining property of the human allele, resistance to sclerostin.

Limitations: Two mutant alleles differ from human heterozygosity. Cranial-nerve morbidity was not evaluated, so absence of that phenotype cannot be inferred. Background differences and different transgene promoters/expression levels limit cross-inhibitor comparisons.

Readouts

Bone response to osteocytic SOST overexpression

Direction: UNCHANGED

Interpretation: The main whole-body and selected bone endpoints did not show significant SOST-induced reductions in HBM mice, unlike controls. This is resistance in specified readouts, not proof of zero response in every microarchitectural parameter.

Show evidence (1 reference)

PMID:25808845 SUPPORT Model Organism

"We observed that the (8kb) Dmp1-SOST transgene significantly lowered whole-body bone mineral density (BMD), bone mineral content (BMC), femoral and vertebral trabecular bone volume fraction (BV/TV), and periosteal bone-formation rate (BFR) in wild-type mice but not in mice with Lrp5 p.G171V and..."

Abstract summary of specified endpoints; full text reports some residual architectural effects.

Show evidence (1 reference)

PMID:25808845 SUPPORT Model Organism

"We previously reported the creation of two Lrp5 HBM knock-in mouse models, in which the human p.A214V or p.G171V missense mutations were knocked into the endogenous Lrp5 locus."

Establishes that these are knock-ins of the human disease alleles at the endogenous locus, which is what makes them informative for this node.

Lrp5 p.A214V knock-in mouse

The 2015 inhibitor-challenge study used homozygous A214V knock-in mice. Endogenous-locus expression preserves regulatory context but differs from the usual heterozygous human genotype. Skeletal responses depend on inhibitor, site and sex.

Species

Mouse

Genotype

Homozygous Lrp5 p.A214V knock-in at the endogenous locus, crossed with SOST- or Dkk1-overexpressing transgenes

Publication

PMID:25808845

Pathograph links

LRP5 Gain-of-Function Variation partially recapitulates fidelity: moderate observes: organism Reproduces sclerostin resistance but remains more sensitive than G171V to DKK1. Under DKK1 challenge, A214V whole-body aBMD fell by approximately 11–14%, with site-specific effects.

Limitations: Two mutant alleles differ from human heterozygosity. Cranial-nerve morbidity was not evaluated, so absence of that phenotype cannot be inferred. Background differences and different transgene promoters/expression levels limit cross-inhibitor comparisons.

Show evidence (1 reference)

PMID:25808845 SUPPORT Model Organism

"The (2.3kb) Col1a1-Dkk1 transgene significantly lowered whole-body BMD, BMC, and vertebral BV/TV in wild-type mice and affected p.A214V mice more than p.G171V mice."

Documents the allele-specific difference in DKK1 sensitivity that limits how far this model generalises.

Conditional Lrp5 HBM with Wls deletion in late osteoblasts and osteocytes

Tests whether intracellular retention of G171V permits bone accrual when Wnt secretion is impaired. Severe Wls-associated osteopenia persisted with either HBM allele; some male bone-mineral-content endpoints showed partial effects.

Species

Mouse

Genotype

Dmp1-Cre activation of conditional G171V or A214V Lrp5 alleles with conditional Wls deletion

Publication

PMID:42113468

Pathograph links

Enhanced Canonical Wnt Signaling in Bone-Forming Cells partially recapitulates fidelity: moderate observes: organism Perturbation tests the dependence of HBM behavior on the ligand-secretion environment.

Limitations: Wls deletion can change resorption and intracellular ligand positioning; these confound a simple inference about receptor localization. This is an engineered compound genotype, not isolated human LRP5 disease.

Show evidence (1 reference)

PMID:42113468 SUPPORT Model Organism

"Wls-deleted mice exhibited a severe low bone mass phenotype whether G171V or A214V was present or not."

Conditional Dmp1-Cre experiments constrain a ligand-independent or intracellular-retention explanation; altered resorption and intracellular ligand localization remain potential confounders.

Show evidence (1 reference)

PMID:42113468 SUPPORT Model Organism

"Wls-deleted mice exhibited a severe low bone mass phenotype whether G171V or A214V was present or not."

Conditional Dmp1-Cre experiments constrain a ligand-independent or intracellular-retention explanation; altered resorption and intracellular ligand localization remain potential confounders.

{ }

Source YAML

click to show

name: Autosomal Dominant Osteopetrosis Type I
creation_date: '2026-09-06T15:45:00Z'
category: Mendelian
description: 'Autosomal dominant osteopetrosis type I (ADO1), commonly called LRP5 high bone mass or Worth-type endosteal hyperostosis, is an inherited sclerosing bone disorder associated with heterozygous activating LRP5 variants. Many established alleles affect the first extracellular beta-propeller and reduce inhibition by sclerostin or DKK1, enhancing Wnt-dependent bone accrual. The spectrum includes in-frame insertions, and a cytoplasmic variant has been reported without functional confirmation. Inhibitor resistance and effects on bone surfaces vary by allele; the evidence does not establish universal ligand-independent receptor activation. Increased formation and, in some genotypes, reduced resorptive responses contribute to the phenotype.

  Skull and long-bone cortical thickening, high bone mineral density, mandibular enlargement and palatal tori are characteristic. Many individuals have few symptoms. Cranial nerve compression, posterior fossa crowding and intracranial hypertension can cause substantial morbidity, sometimes beginning in childhood. Unlike classical resorption-defect osteopetrosis, increased fracture susceptibility and marrow failure are not characteristic, although fractures have been reported. The modern high-bone-mass designation distinguishes the biology while preserving the historical MONDO ADO1 identity.'
synonyms:
- autosomal dominant osteopetrosis type 1
- osteopetrosis, autosomal dominant, type 1
- OPTA1
- LRP5 high bone mass
- LRP5 HBM
- Worth disease
- Worth-type autosomal dominant endosteal hyperostosis
- autosomal dominant osteosclerosis
- LRP5 osteopetrosis
disease_term:
  preferred_term: autosomal dominant osteopetrosis 1
  term:
    id: MONDO:0011877
    label: autosomal dominant osteopetrosis 1
parents:
- Sclerosing Bone Dysplasias
inheritance:
- name: Autosomal Dominant
  description: Heterozygous LRP5 activating variants segregate as an autosomal dominant trait. Clinical severity varies within families; absence of symptoms is not equivalent to absence of skeletal changes. Historical untyped osteopetrosis cohorts do not provide LRP5-specific penetrance estimates. Recessive loss-of-function LRP5 variants cause the distinct osteoporosis-pseudoglioma syndrome.
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  evidence:
  - reference: PMID:12054167
    reference_title: Localization of the gene causing autosomal dominant osteopetrosis type I to chromosome 11q12-13.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Linkage analysis in two families with ADOI from Danish origin enabled us to assign the disease-causing gene to chromosome 11q12-13.
    explanation: Dominant segregation in two multigenerational families localised the ADO1 locus to the interval that contains LRP5.
  - reference: PMID:29208525
    reference_title: 'Novel familial mutation of LRP5 causing high bone mass: Genetic analysis, clinical presentation, and characterization of bone matrix mineralization.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In both individuals, we detected a novel heterozygous duplication of six basepairs in the LRP5 gene, resulting in an insertion of two amino acids, very likely associated with a gain-of-function.
    explanation: Affected mother and daughter had a heterozygous in-frame duplication; the report proposes gain of function rather than measuring receptor activity.
prevalence:
- population: Worldwide, cases reported in the literature
  measure_type: CASES_IN_LITERATURE
  notes: A 2023 historical review assembled 155 clinically described cases, of whom 64 had genetic testing. This is a literature count across changing terminology and ascertainment, not a population prevalence estimate or a genetically confirmed carrier cohort.
  evidence:
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Including the present case, 155 patients have been reported to date.
    explanation: Historical literature count, including molecularly untested cases; no population denominator.
    quote_role: REVIEW_SYNTHESIS
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: The available literature shows that this rare bone disorder is characterized by radiographically evident and generalized endosteal hyperostosis
    explanation: The review explicitly calls the disorder rare. The literature count does not independently establish an ultra-rare population threshold.
  prevalence_class: RARE
genetic:
- name: LRP5
  notes: LRP5 encodes a Wnt co-receptor. Established high-bone-mass alleles include D111Y, G171R, G171V, A214T, A214V, A242T and T253I, concentrated in the first extracellular beta-propeller. The variant spectrum also includes a two-amino-acid insertion. A 2023 report associated cytoplasmic R1414S with radiographic cortical thickening in a father and son whose DXA measurements were normal; that study used segregation and computational predictions without a functional assay. R1414S should not be assumed to share the experimentally demonstrated inhibitor-resistance mechanism of canonical extracellular alleles. Effects on sclerostin, DKK1 and trafficking differ by allele. Recessive loss-of-function disease has the opposite skeletal phenotype.
  gene_term:
    preferred_term: LRP5
    term:
      id: hgnc:6697
      label: LRP5
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  evidence:
  - reference: PMID:12579474
    reference_title: Six novel missense mutations in the LDL receptor-related protein 5 (LRP5) gene in different conditions with an increased bone density.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Thirteen of these were confirmed as polymorphisms, but six novel missense mutations (D111Y, G171R, A214T, A214V, A242T, and T253I) are most likely disease causing.
    explanation: Identifies the LRP5 missense alleles found in patients ascertained with increased bone density including osteopetrosis type I.
  - reference: PMID:12579474
    reference_title: Six novel missense mutations in the LDL receptor-related protein 5 (LRP5) gene in different conditions with an increased bone density.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We performed mutation analysis of the LRP5 gene in 10 families or isolated patients with different conditions with an increased bone density, including endosteal hyperostosis, Van Buchem disease, autosomal dominant osteosclerosis, and osteopetrosis type I.
    explanation: Establishes that osteopetrosis type I was among the high-bone-density conditions in which LRP5 was screened, linking the gene to this entry's disease.
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: LRP5 high bone mass (HBM) is an autosomal dominant endosteal hyperostosis caused by mutations of the low-density lipoprotein receptor-related protein 5 (LRP5) gene.
    explanation: Confirms LRP5 as the causative gene under the disorder's modern designation.
    quote_role: REVIEW_SYNTHESIS
  - reference: PMID:20855225
    reference_title: 'Genetics of bone diseases: Paget''s disease, fibrous dysplasia, osteopetrosis, and osteogenesis imperfecta.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: The identification of LRP5 gain-of-function mutations in autosomal dominant osteopetrosis type I prompted a revision of the classification scheme, and this form is now being included among the high-bone-mass diseases.
    explanation: States both the gain-of-function mechanism and the resulting reclassification of ADO1 out of the osteopetroses, which is the framing this whole entry rests on and was previously asserted only in prose.
    quote_role: REVIEW_SYNTHESIS
  - reference: PMID:29208525
    reference_title: 'Novel familial mutation of LRP5 causing high bone mass: Genetic analysis, clinical presentation, and characterization of bone matrix mineralization.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In both individuals, we detected a novel heterozygous duplication of six basepairs in the LRP5 gene, resulting in an insertion of two amino acids, very likely associated with a gain-of-function.
    explanation: Affected mother and daughter had a heterozygous in-frame duplication; the report proposes gain of function rather than measuring receptor activity.
  - reference: PMID:36971833
    reference_title: 'Novel mutation in LRP5 gene cause rare osteosclerosis: cases studies and literature review.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The mutation (c.4240C > A, p.R1414S) of patients 2 and 3 in this study locates in exon 20 of LRP5
    explanation: Clinical report of a cytoplasmic variant in a father and son. Functional Wnt activation was proposed from sequence location rather than measured.
pathophysiology:
- name: LRP5 Gain-of-Function Variation
  biological_scale: MOLECULAR
  description: Heterozygous LRP5 activating variants cause inherited high bone mass. Many established missense variants cluster in the first extracellular beta-propeller; in-frame insertion alleles also occur. Tested HBM receptor variants have reduced binding or sensitivity to extracellular antagonists. This region participates in a receptor whose ligand binding, trafficking and inhibition are interdependent; it is not simply an isolated non-Wnt-binding brake. The reported cytoplasmic R1414S association has not been functionally shown to use the same mechanism.
  gene:
    preferred_term: LRP5
    term:
      id: hgnc:6697
      label: LRP5
  evidence:
  - reference: PMID:12579474
    reference_title: Six novel missense mutations in the LDL receptor-related protein 5 (LRP5) gene in different conditions with an increased bone density.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Like the previously reported mutation (G171V) that causes the high-bone-mass phenotype, all mutations are located in the aminoterminal part of the gene, before the first epidermal growth factor-like domain.
    explanation: First-propeller clustering in the alleles studied in 2003; this is not an exhaustive statement about all subsequently reported variants.
  - reference: PMID:29208525
    reference_title: 'Novel familial mutation of LRP5 causing high bone mass: Genetic analysis, clinical presentation, and characterization of bone matrix mineralization.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In both individuals, we detected a novel heterozygous duplication of six basepairs in the LRP5 gene, resulting in an insertion of two amino acids, very likely associated with a gain-of-function.
    explanation: Affected mother and daughter had a heterozygous in-frame duplication; the report proposes gain of function rather than measuring receptor activity.
  - reference: PMID:17052975
    reference_title: LRP5 mutations linked to high bone mass diseases cause reduced LRP5 binding and inhibition by SOST.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Here we show that LRP5 HBM mutant proteins exhibit reduced binding to a secreted bone-specific LRP5 antagonist, SOST, and consequently are more refractory to inhibition by SOST.
    explanation: Receptor assays support reduced antagonist sensitivity, not complete loss of all feedback or ligand-independent activation.
  downstream:
  - target: Enhanced Canonical Wnt Signaling in Bone-Forming Cells
    description: Reduced antagonist sensitivity can enhance Wnt signaling. The magnitude and inhibitor specificity depend on the allele.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:17052975
      reference_title: LRP5 mutations linked to high bone mass diseases cause reduced LRP5 binding and inhibition by SOST.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: Here we show that LRP5 HBM mutant proteins exhibit reduced binding to a secreted bone-specific LRP5 antagonist, SOST, and consequently are more refractory to inhibition by SOST.
      explanation: Receptor assays support reduced antagonist sensitivity, not complete loss of all feedback or ligand-independent activation.
- name: Enhanced Canonical Wnt Signaling in Bone-Forming Cells
  biological_scale: CELLULAR
  description: LRP5 HBM variants can enhance canonical Wnt signaling by reducing inhibition by sclerostin and, variably, DKK1. This does not imply complete loss of feedback or constitutive ligand-independent signaling. Homozygous G171V and A214V mice resisted many skeletal effects of SOST overexpression, but some architectural responses remained; A214V was more responsive to DKK1 than G171V. In conditional mice, neither allele rescued severe osteopenia caused by Wls deletion in late osteoblasts/osteocytes, limiting a proposed autonomous intracellular-signaling explanation.
  cell_types:
  - preferred_term: osteoblast
    term:
      id: CL:0000062
      label: osteoblast
  biological_processes:
  - preferred_term: canonical Wnt signaling pathway
    modifier: INCREASED
    term:
      id: GO:0060070
      label: canonical Wnt signaling pathway
  evidence:
  - reference: PMID:18328982
    reference_title: Sclerosing bone disorders.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Other less common recessive or dominant sclerosing disorders, such as endosteal hyperostosis, sclerostosis, van Buchen disease and high bone mass syndrome, are due to mutations in two genes (LRP5 and SOST) of the Wnt pathway that induce increased osteoblast activity.
    explanation: Attributes the increased osteoblast activity in this disease group to Wnt pathway gene mutations.
    quote_role: REVIEW_SYNTHESIS
  - reference: PMID:17052975
    reference_title: LRP5 mutations linked to high bone mass diseases cause reduced LRP5 binding and inhibition by SOST.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Here we show that LRP5 HBM mutant proteins exhibit reduced binding to a secreted bone-specific LRP5 antagonist, SOST, and consequently are more refractory to inhibition by SOST.
    explanation: Receptor assays support reduced antagonist sensitivity, not complete loss of all feedback or ligand-independent activation.
  - reference: PMID:42113468
    reference_title: Different Lrp5-HBM mutations induce magnitude- and surface-selective effects that are not explained by receptor trafficking.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: Wls-deleted mice exhibited a severe low bone mass phenotype whether G171V or A214V was present or not.
    explanation: Conditional Dmp1-Cre experiments constrain a ligand-independent or intracellular-retention explanation; altered resorption and intracellular ligand localization remain potential confounders.
  downstream:
  - target: Increased Osteoblastic Bone Formation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:16251418
      reference_title: Osteoclasts from patients with autosomal dominant osteopetrosis type I caused by a T253I mutation in low-density lipoprotein receptor-related protein 5 are normal in vitro, but have decreased resorption capacity in vivo.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Patients with a T253I mutation in LRP5 have a high bone mass phenotype, characterized by increased mineralizing surface index but abnormally low numbers of small osteoclasts.
      explanation: The T253I paper summarizes prior patient histomorphometry in its introduction; this is not a new measurement of increased formation in its T3 experiment.
      quote_role: BACKGROUND
    description: Enhanced Wnt signaling promotes bone accrual through osteoblast-lineage activity, with effects varying by surface, genotype and age.
  - target: Reduced Osteoclast Number and Resorptive Response
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Altered osteoblast-lineage support is one proposed explanation for the T253I in vivo/culture discrepancy. RANKL/OPG or other mediators have not been shown to carry this causal effect in patients.
    evidence:
    - reference: PMID:16251418
      reference_title: Osteoclasts from patients with autosomal dominant osteopetrosis type I caused by a T253I mutation in low-density lipoprotein receptor-related protein 5 are normal in vitro, but have decreased resorption capacity in vivo.
      supports: SUPPORT
      directness: INDIRECT
      evidence_source: OTHER
      snippet: We speculate that the mutations causing ADOI alter the osteoblastic phenotype toward a smaller potential for supporting osteoclastogenesis.
      explanation: Authors explicitly speculate about osteoblastic support; mediator identity and causal direction were not established by intervention.
      quote_role: PRIMARY_RESULT
- name: Increased Osteoblastic Bone Formation
  biological_scale: TISSUE
  description: Increased bone-forming activity contributes to high bone mass, with genotype-, surface- and age-dependent effects. Prior T253I histomorphometry reported increased mineralizing surface, while the later T3 study found normal baseline formation markers and a normal stimulated formation response. Dynamic labeling in HBM knock-in mice demonstrates increased formation on selected surfaces. A normal T3 response alone is not evidence of elevated formation, and mature patient bone does not necessarily continue accumulating rapidly throughout adulthood.
  cell_types:
  - preferred_term: osteoblast
    term:
      id: CL:0000062
      label: osteoblast
  biological_processes:
  - preferred_term: bone mineralization
    modifier: INCREASED
    term:
      id: GO:0030282
      label: bone mineralization
  evidence:
  - reference: PMID:16251418
    reference_title: Osteoclasts from patients with autosomal dominant osteopetrosis type I caused by a T253I mutation in low-density lipoprotein receptor-related protein 5 are normal in vitro, but have decreased resorption capacity in vivo.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Patients with a T253I mutation in LRP5 have a high bone mass phenotype, characterized by increased mineralizing surface index but abnormally low numbers of small osteoclasts.
    explanation: The T253I paper summarizes prior patient histomorphometry in its introduction; this is not a new measurement of increased formation in its T3 experiment.
    quote_role: BACKGROUND
  - reference: PMID:42113468
    reference_title: Different Lrp5-HBM mutations induce magnitude- and surface-selective effects that are not explained by receptor trafficking.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: On the endocortical surface, mineralizing surface and bone formation rates were increased in all 3 HBM genotypes compared to controls, at both time points, with the exception of BFR/BS in heterozygous G171V/A214V mice at the later time point.
    explanation: Global homozygous or compound-mutant mice; dynamic histomorphometry is surface- and time-dependent and differs from the heterozygous human genotype.
  downstream:
  - target: Excess Skeletal Bone Accrual
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:18328982
      reference_title: Sclerosing bone disorders.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Osteocondensation can also be related to increased bone formation.
      explanation: States the formation-driven route to increased bone density that this entry's pathograph follows.
      quote_role: REVIEW_SYNTHESIS
- name: Reduced Osteoclast Number and Resorptive Response
  biological_scale: CELLULAR
  description: In studied T253I patients, historical histology showed fewer small osteoclasts and an in vivo T3 challenge produced an attenuated resorption response despite a normal formation response. Patient CD14-derived osteoclasts supplied with RANKL and M-CSF were normal for the tested culture endpoints. These results favor a context-dependent defect but do not exclude every cell-intrinsic contribution. The clinical response and osteoclast-number phenotype should not be generalized to every LRP5 HBM allele.
  cell_types:
  - preferred_term: osteoclast
    term:
      id: CL:0000092
      label: osteoclast
  biological_processes:
  - preferred_term: bone resorption
    modifier: DECREASED
    term:
      id: GO:0045453
      label: bone resorption
  evidence:
  - reference: PMID:16251418
    reference_title: Osteoclasts from patients with autosomal dominant osteopetrosis type I caused by a T253I mutation in low-density lipoprotein receptor-related protein 5 are normal in vitro, but have decreased resorption capacity in vivo.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: We found normal osteoclastogenesis, expression of osteoclast markers, morphology, and localization of proteins involved in bone resorption, such as ClC-7 and cathepsin K.
    explanation: Patient monocytes differentiated under supplied RANKL/M-CSF showed normal tested markers and morphology. This culture environment bypasses some physiological support signals.
  - reference: PMID:16251418
    reference_title: Osteoclasts from patients with autosomal dominant osteopetrosis type I caused by a T253I mutation in low-density lipoprotein receptor-related protein 5 are normal in vitro, but have decreased resorption capacity in vivo.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: These data demonstrate that ADOI osteoclasts are normal with respect to all aspects investigated in vitro.
    explanation: Negative results are bounded to the endpoints and culture conditions tested; they do not prove that all osteoclast-intrinsic pathways are unaffected.
  - reference: PMID:16251418
    reference_title: Osteoclasts from patients with autosomal dominant osteopetrosis type I caused by a T253I mutation in low-density lipoprotein receptor-related protein 5 are normal in vitro, but have decreased resorption capacity in vivo.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We found attenuated resorptive response to T3 stimulation, despite a normal bone formation response, in alignment with the reduced number of osteoclasts in vivo.
    explanation: T253I clinical stimulation study; the displayed resorption comparison included six patients and nine controls, rather than every enrolled participant.
  downstream:
  - target: Excess Skeletal Bone Accrual
    causal_link_type: DIRECT
    description: Reduced resorptive responses may contribute to high bone mass in the studied T253I context; their mediator and contribution relative to formation remain unresolved.
    evidence:
    - reference: PMID:16251418
      reference_title: Osteoclasts from patients with autosomal dominant osteopetrosis type I caused by a T253I mutation in low-density lipoprotein receptor-related protein 5 are normal in vitro, but have decreased resorption capacity in vivo.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Patients with a T253I mutation in LRP5 have a high bone mass phenotype, characterized by increased mineralizing surface index but abnormally low numbers of small osteoclasts.
      explanation: Prior patient histology summarized in the introduction; this association does not establish osteoblast-to-osteoclast mediation.
      quote_role: BACKGROUND
  mechanism_confidence: PROVISIONAL
- name: Excess Skeletal Bone Accrual
  biological_scale: TISSUE
  description: High bone mass affects the skull and long-bone cortices, with variable trabecular and cortical remodeling. Human skull tissue from an insertion-allele carrier showed lamellar organization and normal mineralization with region-specific remodeling. Fractures can occur, but excess fracture susceptibility and marrow failure are not characteristic of LRP5 HBM.
  evidence:
  - reference: PMID:12054167
    reference_title: Localization of the gene causing autosomal dominant osteopetrosis type I to chromosome 11q12-13.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Within the autosomal dominant form of osteopetrosis, the radiological type I (ADOI) is characterized by a generalized osteosclerosis, most pronounced at the cranial vault.
    explanation: Defines the radiological hallmark and its cranial predominance, which is what drives the neurological consequences downstream.
  - reference: PMID:29208525
    reference_title: 'Novel familial mutation of LRP5 causing high bone mass: Genetic analysis, clinical presentation, and characterization of bone matrix mineralization.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Our findings indicate normal morphology of osteoclasts and osteoblasts as well as normal mineralization in skull bone in LRP5-HBM.
    explanation: Histology and mineralization measurements from surgically removed occipital bone in one insertion-allele carrier; not proof of identical architecture at all sites or in all patients.
  downstream:
  - target: Cranial Foramina Narrowing
    description: Hyperostotic cranial bone can encroach on nerve passages.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:37659026
      reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: In summary, neurological involvement may occur because of nerve tissue compression by hyperostotic bone, cerebellar disturbances due to a reduction in size of the posterior cranial fossa or tonsillar herniation, and chronic intracranial hypertension
      explanation: Distinguishes direct nerve compression from reduced posterior-fossa space and pressure-related complications.
      quote_role: REVIEW_SYNTHESIS
  - target: Increased bone mineral density
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:37659026
      reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Dual-energy X-ray absorptiometry (DEXA) scan revealed elevated bone mass.
      explanation: Densitometric confirmation of the sclerosis in a genetically confirmed case.
  - target: Generalized osteosclerosis
    description: The radiographic phenotype records diffuse excess bone density.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:12054167
      reference_title: Localization of the gene causing autosomal dominant osteopetrosis type I to chromosome 11q12-13.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Within the autosomal dominant form of osteopetrosis, the radiological type I (ADOI) is characterized by a generalized osteosclerosis, most pronounced at the cranial vault.
      explanation: Defines the radiological hallmark and its cranial predominance, which is what drives the neurological consequences downstream.
  - target: Craniofacial hyperostosis
    description: Excess bone accrual can thicken cranial and facial bones.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:29208525
      reference_title: 'Novel familial mutation of LRP5 causing high bone mass: Genetic analysis, clinical presentation, and characterization of bone matrix mineralization.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Our findings indicate normal morphology of osteoclasts and osteoblasts as well as normal mineralization in skull bone in LRP5-HBM.
      explanation: Histology and mineralization measurements from surgically removed occipital bone in one insertion-allele carrier; not proof of identical architecture at all sites or in all patients.
  - target: Torus palatinus
    description: Localized palatal bone overgrowth produces a torus.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:37659026
      reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Facial changes and torus palatinus were observed in 61% and 41% of cases, respectively.
      explanation: Quantifies torus palatinus at 41% of assembled cases.
      quote_role: REVIEW_SYNTHESIS
  - target: Mandibular enlargement
    description: Craniofacial bone accrual can enlarge the mandible.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:36971833
      reference_title: 'Novel mutation in LRP5 gene cause rare osteosclerosis: cases studies and literature review.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: 'The clinical phenotypes mainly included: mandibular enlargement (51/57), prominence of torus palatinus (44/62), bone pain (21/59), headache (12/51), hearing loss (9/54), facial nerve palsy (7/56), and vision loss (2/53).'
      explanation: Literature synthesis uses a different denominator for each recorded feature; these are selected published cases, not prospective carrier risks.
      quote_role: REVIEW_SYNTHESIS
  - target: Bone pain
    description: Pain accompanies skeletal overgrowth in some patients; the specific nociceptive mediator is unresolved.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Reduced Intracranial Space
    description: Skull thickening can reduce available intracranial space.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:37659026
      reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: In summary, neurological involvement may occur because of nerve tissue compression by hyperostotic bone, cerebellar disturbances due to a reduction in size of the posterior cranial fossa or tonsillar herniation, and chronic intracranial hypertension
      explanation: Distinguishes direct nerve compression from reduced posterior-fossa space and pressure-related complications.
      quote_role: REVIEW_SYNTHESIS
  - target: Spinal canal stenosis
    description: Excess vertebral bone may narrow the spinal canal in reported cases.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:37659026
      reference_title: "LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Two related Japanese patients presented with chronic occipital headache and spinal canal stenosis causing pain and paresthesias in the upper limb
      explanation: Historical literature synthesis; no genotype-specific frequency estimate.
      quote_role: REVIEW_SYNTHESIS
- name: Cranial Foramina Narrowing
  biological_scale: TISSUE
  description: 'Hyperostotic bone can narrow cranial nerve passages and cause hearing loss, facial palsy or trigeminal symptoms. The timing is variable: congenital hearing impairment was reported in an insertion-allele carrier. Anosmia has been reported, but its exact anatomic mediator was not demonstrated in that case.'
  evidence:
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: In summary, neurological involvement may occur because of nerve tissue compression by hyperostotic bone, cerebellar disturbances due to a reduction in size of the posterior cranial fossa or tonsillar herniation, and chronic intracranial hypertension
    explanation: Distinguishes direct nerve compression from reduced posterior-fossa space and pressure-related complications.
    quote_role: REVIEW_SYNTHESIS
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: At age 35, external hearing aids were placed due to complete, bilateral, and mixed hearing loss caused by the narrowing of internal and external acoustic meati.
    explanation: Index A242T case with anatomically described auditory canal narrowing.
  downstream:
  - target: Hearing impairment
    description: Auditory canal narrowing can contribute to hearing impairment.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:37659026
      reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: At age 35, external hearing aids were placed due to complete, bilateral, and mixed hearing loss caused by the narrowing of internal and external acoustic meati.
      explanation: Index A242T case with anatomically described auditory canal narrowing.
  - target: Anosmia
    description: Olfactory dysfunction may relate to cranial hyperostosis; cribriform compression was not directly established.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:37659026
      reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: A 44-year-old Caucasian woman with torus palatinus complained of headache, hypo-/anosmia, and complete mixed deafness.
      explanation: Documents hyposmia/anosmia in a genetically confirmed LRP5 case.
  - target: Facial palsy
    description: Facial nerve compression can produce palsy.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:37659026
      reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: In summary, neurological involvement may occur because of nerve tissue compression by hyperostotic bone, cerebellar disturbances due to a reduction in size of the posterior cranial fossa or tonsillar herniation, and chronic intracranial hypertension
      explanation: Distinguishes direct nerve compression from reduced posterior-fossa space and pressure-related complications.
      quote_role: REVIEW_SYNTHESIS
  - target: Trigeminal neuralgia
    description: Nerve compression may contribute to neuralgia; bony crowding and neurovascular conflict can coexist.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:37659026
      reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: In summary, neurological involvement may occur because of nerve tissue compression by hyperostotic bone, cerebellar disturbances due to a reduction in size of the posterior cranial fossa or tonsillar herniation, and chronic intracranial hypertension
      explanation: Distinguishes direct nerve compression from reduced posterior-fossa space and pressure-related complications.
      quote_role: REVIEW_SYNTHESIS
  - target: Visual impairment
    description: Optic nerve compression is reported in the historical clinical literature.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:37659026
      reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: reported a case presenting with progressive unilateral compression of the optic, trigeminal, and facial nerves
      explanation: Review of a prior case of cranial nerve compression.
      quote_role: REVIEW_SYNTHESIS
- name: Reduced Intracranial Space
  biological_scale: TISSUE
  description: Cranial hyperostosis may reduce posterior fossa capacity or intracranial compliance, with tonsillar herniation and raised pressure. This route is distinct from direct compression of individual nerves in foramina.
  evidence:
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: In summary, neurological involvement may occur because of nerve tissue compression by hyperostotic bone, cerebellar disturbances due to a reduction in size of the posterior cranial fossa or tonsillar herniation, and chronic intracranial hypertension
    explanation: Distinguishes direct nerve compression from reduced posterior-fossa space and pressure-related complications.
    quote_role: REVIEW_SYNTHESIS
  downstream:
  - target: Increased intracranial pressure
    description: Reported pressure/crowding-related neurologic complication.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:37659026
      reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: In summary, neurological involvement may occur because of nerve tissue compression by hyperostotic bone, cerebellar disturbances due to a reduction in size of the posterior cranial fossa or tonsillar herniation, and chronic intracranial hypertension
      explanation: Distinguishes direct nerve compression from reduced posterior-fossa space and pressure-related complications.
      quote_role: REVIEW_SYNTHESIS
  - target: Papilledema
    description: Reported pressure/crowding-related neurologic complication.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:37659026
      reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: In summary, neurological involvement may occur because of nerve tissue compression by hyperostotic bone, cerebellar disturbances due to a reduction in size of the posterior cranial fossa or tonsillar herniation, and chronic intracranial hypertension
      explanation: Distinguishes direct nerve compression from reduced posterior-fossa space and pressure-related complications.
      quote_role: REVIEW_SYNTHESIS
  - target: Chiari malformation
    description: Reported pressure/crowding-related neurologic complication.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:37659026
      reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: In summary, neurological involvement may occur because of nerve tissue compression by hyperostotic bone, cerebellar disturbances due to a reduction in size of the posterior cranial fossa or tonsillar herniation, and chronic intracranial hypertension
      explanation: Distinguishes direct nerve compression from reduced posterior-fossa space and pressure-related complications.
      quote_role: REVIEW_SYNTHESIS
  - target: Headache
    description: Reported pressure/crowding-related neurologic complication.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:37659026
      reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: In summary, neurological involvement may occur because of nerve tissue compression by hyperostotic bone, cerebellar disturbances due to a reduction in size of the posterior cranial fossa or tonsillar herniation, and chronic intracranial hypertension
      explanation: Distinguishes direct nerve compression from reduced posterior-fossa space and pressure-related complications.
      quote_role: REVIEW_SYNTHESIS
phenotypes:
- category: Skeletal
  name: Generalized osteosclerosis
  description: 'Diffuse increase in bone density on plain radiographs, maximal at the cranial vault. This is the defining radiological finding and the basis of the historical "type I" designation.

    '
  phenotype_term:
    preferred_term: Generalized osteosclerosis
    term:
      id: HP:0005789
      label: Generalized osteosclerosis
  evidence:
  - reference: PMID:12054167
    reference_title: Localization of the gene causing autosomal dominant osteopetrosis type I to chromosome 11q12-13.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Within the autosomal dominant form of osteopetrosis, the radiological type I (ADOI) is characterized by a generalized osteosclerosis, most pronounced at the cranial vault.
    explanation: The defining radiological criterion for ADO1.
- category: Skeletal
  name: Increased bone mineral density
  description: DXA is usually elevated. In a literature synthesis, lumbar-spine values were increased in 40/43 evaluated cases and hip values in 26/31. Radiographic cortical thickening with normal DXA was reported in R1414S carriers, whose variant mechanism remains untested. These selected reports do not estimate carrier penetrance.
  phenotype_term:
    preferred_term: Increased bone mineral density
    term:
      id: HP:0011001
      label: Increased bone mineral density
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Dual-energy X-ray absorptiometry (DEXA) scan revealed elevated bone mass.
    explanation: Densitometric confirmation in a genetically confirmed LRP5 case.
  - reference: PMID:36971833
    reference_title: 'Novel mutation in LRP5 gene cause rare osteosclerosis: cases studies and literature review.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: the proportion of patients with elevated BMD at lumbar spine and hip were 40/43, 26/31, respectively
    explanation: Measurement-specific denominators in a literature synthesis; reports overlap with other reviews and should not be pooled as independent samples.
    quote_role: REVIEW_SYNTHESIS
- category: Craniofacial
  name: Craniofacial hyperostosis
  description: Thickening of skull and facial bones can alter appearance. The historical review recorded facial changes in 93/153 cases with reported status (61%); this broader observation is not a direct frequency measurement of the specific HPO hyperostosis finding.
  phenotype_term:
    preferred_term: Craniofacial hyperostosis
    term:
      id: HP:0004493
      label: Craniofacial hyperostosis
  evidence:
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Facial changes and torus palatinus were observed in 61% and 41% of cases, respectively.
    explanation: Facial changes were reported in 93/153 assessable historical cases, without a standardized hyperostosis endpoint.
    quote_role: REVIEW_SYNTHESIS
  - reference: PMID:29208525
    reference_title: 'Novel familial mutation of LRP5 causing high bone mass: Genetic analysis, clinical presentation, and characterization of bone matrix mineralization.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: increased calvarial thickness, and thickened cortices of the long bones but no history of fractures
    explanation: Cranial and long-bone thickening in two molecularly characterized family members.
- category: Craniofacial
  name: Torus palatinus
  description: Bony exostosis of the hard palate. One historical review reported 58/140 assessable cases (41%); another synthesis reported 44/62 (71%). Different ascertainment and missing data preclude a single carrier-frequency estimate.
  phenotype_term:
    preferred_term: Torus palatinus
    term:
      id: HP:0100789
      label: Torus palatinus
  evidence:
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Facial changes and torus palatinus were observed in 61% and 41% of cases, respectively.
    explanation: Tori were documented in 58 of 140 cases with ascertainable status, not 41% of all 155 cases.
    quote_role: REVIEW_SYNTHESIS
  - reference: PMID:36971833
    reference_title: 'Novel mutation in LRP5 gene cause rare osteosclerosis: cases studies and literature review.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: 'The clinical phenotypes mainly included: mandibular enlargement (51/57), prominence of torus palatinus (44/62), bone pain (21/59), headache (12/51), hearing loss (9/54), facial nerve palsy (7/56), and vision loss (2/53).'
    explanation: Literature synthesis uses a different denominator for each recorded feature; these are selected published cases, not prospective carrier risks.
    quote_role: REVIEW_SYNTHESIS
- category: Neurological
  name: Hearing impairment
  description: Hearing impairment can be conductive, sensorineural or mixed. Onset and progression vary; congenital impairment requiring cochlear implantation was reported in an insertion-allele carrier, while the A242T index case had adult complete mixed deafness.
  phenotype_term:
    preferred_term: Hearing impairment
    term:
      id: HP:0000365
      label: Hearing impairment
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:12054167
    reference_title: Localization of the gene causing autosomal dominant osteopetrosis type I to chromosome 11q12-13.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The patients are often asymptomatic but some suffer from pain and hearing loss.
    explanation: Reports hearing loss among symptoms; the 9/54 frequency estimate comes from the later literature synthesis.
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: A 44-year-old Caucasian woman with torus palatinus complained of headache, hypo-/anosmia, and complete mixed deafness.
    explanation: Documents mixed deafness in a genetically confirmed case.
  - reference: PMID:36971833
    reference_title: 'Novel mutation in LRP5 gene cause rare osteosclerosis: cases studies and literature review.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: 'The clinical phenotypes mainly included: mandibular enlargement (51/57), prominence of torus palatinus (44/62), bone pain (21/59), headache (12/51), hearing loss (9/54), facial nerve palsy (7/56), and vision loss (2/53).'
    explanation: Literature synthesis uses a different denominator for each recorded feature; these are selected published cases, not prospective carrier risks.
    quote_role: REVIEW_SYNTHESIS
- category: Neurological
  name: Headache
  phenotype_term:
    preferred_term: Headache
    term:
      id: HP:0002315
      label: Headache
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: A 44-year-old Caucasian woman with torus palatinus complained of headache, hypo-/anosmia, and complete mixed deafness.
    explanation: Documents headache as a presenting neurological complaint.
  - reference: PMID:36971833
    reference_title: 'Novel mutation in LRP5 gene cause rare osteosclerosis: cases studies and literature review.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: 'The clinical phenotypes mainly included: mandibular enlargement (51/57), prominence of torus palatinus (44/62), bone pain (21/59), headache (12/51), hearing loss (9/54), facial nerve palsy (7/56), and vision loss (2/53).'
    explanation: Literature synthesis uses a different denominator for each recorded feature; these are selected published cases, not prospective carrier risks.
    quote_role: REVIEW_SYNTHESIS
- category: Neurological
  name: Anosmia
  description: Reduced or absent olfaction was reported in the A242T index case; no carrier-frequency estimate or direct proof of cribriform-plate compression is available.
  phenotype_term:
    preferred_term: Anosmia
    term:
      id: HP:0000458
      label: Anosmia
  evidence:
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: A 44-year-old Caucasian woman with torus palatinus complained of headache, hypo-/anosmia, and complete mixed deafness.
    explanation: Documents hyposmia/anosmia in a genetically confirmed LRP5 case.
- category: Skeletal
  name: Bone pain
  phenotype_term:
    preferred_term: Bone pain
    term:
      id: HP:0002653
      label: Bone pain
  frequency: FREQUENT
  evidence:
  - reference: PMID:12054167
    reference_title: Localization of the gene causing autosomal dominant osteopetrosis type I to chromosome 11q12-13.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The patients are often asymptomatic but some suffer from pain and hearing loss.
    explanation: Reports pain in symptomatic patients, without quantifying a frequency band.
  - reference: PMID:36971833
    reference_title: 'Novel mutation in LRP5 gene cause rare osteosclerosis: cases studies and literature review.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: 'The clinical phenotypes mainly included: mandibular enlargement (51/57), prominence of torus palatinus (44/62), bone pain (21/59), headache (12/51), hearing loss (9/54), facial nerve palsy (7/56), and vision loss (2/53).'
    explanation: Literature synthesis uses a different denominator for each recorded feature; these are selected published cases, not prospective carrier risks.
    quote_role: REVIEW_SYNTHESIS
- category: Skeletal
  name: Absence of increased fracture rate
  description: 'An increased fracture tendency is not characteristic of LRP5 high bone mass. This distinguishes it from many resorption-defect osteopetroses, but does not imply immunity to fractures: the historical review includes fracture cases.'
  phenotype_term:
    preferred_term: Increased susceptibility to fractures
    term:
      id: HP:0002659
      label: Increased susceptibility to fractures
  frequency: EXCLUDED
  evidence:
  - reference: PMID:12054167
    reference_title: Localization of the gene causing autosomal dominant osteopetrosis type I to chromosome 11q12-13.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: ADOI is the only type of osteopetrosis not associated with an increased fracture rate.
    explanation: The negative annotation concerns excess susceptibility, not the occurrence of any fracture.
- category: Neurological
  name: Papilledema
  description: Papilledema is reported among neurologic complications and can signal raised intracranial pressure.
  phenotype_term:
    preferred_term: Papilledema
    term:
      id: HP:0001085
      label: Papilledema
  evidence:
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Cranial nerve deficits and/or other neurologic complications (e.g., intracranial hypertension, headache, spinal canal stenosis, sensitive neuropathy, papilledema, type I Chiari malformation, nausea and/or vomiting, migraine, and cerebellar tonsillar herniation) were present in 30 patients.
    explanation: Listed among the neurologic complications recorded across the 155-patient review. No per-manifestation frequency is given, only the 19.4% aggregate for neurological involvement, so no frequency is asserted here.
    quote_role: REVIEW_SYNTHESIS
- category: Neurological
  name: Increased intracranial pressure
  description: Raised intracranial pressure is reported as a complication of cranial hyperostosis and crowding, distinct from compression of individual nerves.
  phenotype_term:
    preferred_term: Increased intracranial pressure
    term:
      id: HP:0002516
      label: Increased intracranial pressure
  evidence:
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Cranial nerve deficits and/or other neurologic complications (e.g., intracranial hypertension, headache, spinal canal stenosis, sensitive neuropathy, papilledema, type I Chiari malformation, nausea and/or vomiting, migraine, and cerebellar tonsillar herniation) were present in 30 patients.
    explanation: Listed among the neurologic complications recorded across the 155-patient review. No per-manifestation frequency is given, only the 19.4% aggregate for neurological involvement, so no frequency is asserted here.
    quote_role: REVIEW_SYNTHESIS
- category: Neurological
  name: Chiari malformation
  description: 'Type I Chiari malformation and cerebellar tonsillar herniation are recorded in the review, consistent with reduced posterior fossa volume from vault thickening.

    '
  phenotype_term:
    preferred_term: Chiari malformation
    term:
      id: HP:0002308
      label: Chiari malformation
  evidence:
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Cranial nerve deficits and/or other neurologic complications (e.g., intracranial hypertension, headache, spinal canal stenosis, sensitive neuropathy, papilledema, type I Chiari malformation, nausea and/or vomiting, migraine, and cerebellar tonsillar herniation) were present in 30 patients.
    explanation: Listed among the neurologic complications recorded across the 155-patient review. No per-manifestation frequency is given, only the 19.4% aggregate for neurological involvement, so no frequency is asserted here.
    quote_role: REVIEW_SYNTHESIS
- category: Skeletal
  name: Elevated circulating alkaline phosphatase concentration
  description: ALP was elevated in 5/136 assessable historical cases (3.7%). Normal ALP is common and does not exclude LRP5 high bone mass; the case compilation does not establish population frequency.
  phenotype_term:
    preferred_term: Elevated circulating alkaline phosphatase concentration
    term:
      id: HP:0003155
      label: Elevated circulating alkaline phosphatase concentration
  frequency: VERY_RARE
  evidence:
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Elevated serum ALP levels are present in a minority of patients (3.7%), and facial changes and torus palatinus are not consistent findings, with a prevalence of approximately 61% and 41%, respectively.
    explanation: Five of 136 cases with reported ALP status had elevated values; not five of all 155 cases.
    quote_role: REVIEW_SYNTHESIS
- name: Facial palsy
  category: Neurological
  phenotype_term:
    preferred_term: Facial palsy
    term:
      id: HP:0010628
      label: Facial palsy
  evidence:
  - reference: PMID:36971833
    reference_title: 'Novel mutation in LRP5 gene cause rare osteosclerosis: cases studies and literature review.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: 'The clinical phenotypes mainly included: mandibular enlargement (51/57), prominence of torus palatinus (44/62), bone pain (21/59), headache (12/51), hearing loss (9/54), facial nerve palsy (7/56), and vision loss (2/53).'
    explanation: Literature synthesis uses a different denominator for each recorded feature; these are selected published cases, not prospective carrier risks.
    quote_role: REVIEW_SYNTHESIS
  frequency: OCCASIONAL
  description: Reported in 7/56 assessable cases in a literature synthesis, with variable onset and recurrence.
- name: Mandibular enlargement
  category: Craniofacial
  phenotype_term:
    preferred_term: Mandibular enlargement
    term:
      id: HP:0040309
      label: Increased size of the mandible
  frequency: VERY_FREQUENT
  description: Mandibular enlargement was reported in 51/57 assessable literature cases. This selected-case fraction is not a prospective carrier risk.
  evidence:
  - reference: PMID:36971833
    reference_title: 'Novel mutation in LRP5 gene cause rare osteosclerosis: cases studies and literature review.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: 'The clinical phenotypes mainly included: mandibular enlargement (51/57), prominence of torus palatinus (44/62), bone pain (21/59), headache (12/51), hearing loss (9/54), facial nerve palsy (7/56), and vision loss (2/53).'
    explanation: Literature synthesis uses a different denominator for each recorded feature; these are selected published cases, not prospective carrier risks.
    quote_role: REVIEW_SYNTHESIS
- name: Trigeminal neuralgia
  category: Neurological
  phenotype_term:
    preferred_term: Trigeminal neuralgia
    term:
      id: HP:0100661
      label: Trigeminal neuralgia
  evidence:
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Our patient reported complete and bilateral hearing loss, trigeminal neuralgia, transient facial palsy, and hypo-/anosmia
    explanation: Clinical A242T case; no phenotype-specific frequency estimate.
- name: Visual impairment
  category: Ophthalmological
  phenotype_term:
    preferred_term: Visual impairment
    term:
      id: HP:0000505
      label: Visual impairment
  evidence:
  - reference: PMID:36971833
    reference_title: 'Novel mutation in LRP5 gene cause rare osteosclerosis: cases studies and literature review.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: 'The clinical phenotypes mainly included: mandibular enlargement (51/57), prominence of torus palatinus (44/62), bone pain (21/59), headache (12/51), hearing loss (9/54), facial nerve palsy (7/56), and vision loss (2/53).'
    explanation: Literature synthesis uses a different denominator for each recorded feature; these are selected published cases, not prospective carrier risks.
    quote_role: REVIEW_SYNTHESIS
  frequency: VERY_RARE
  description: Vision loss was reported in 2/53 assessable literature cases. Optic nerve compression is a reported complication, without a prospective risk estimate.
- name: Spinal canal stenosis
  category: Skeletal
  description: Spinal canal narrowing is reported with upper-limb pain and paresthesias in historical cases. Its frequency and genotype-specific risk are not established.
  phenotype_term:
    preferred_term: Spinal canal stenosis
    term:
      id: HP:0003416
      label: Spinal canal stenosis
  evidence:
  - reference: PMID:37659026
    reference_title: "LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Two related Japanese patients presented with chronic occipital headache and spinal canal stenosis causing pain and paresthesias in the upper limb
    explanation: Historical literature synthesis; no genotype-specific frequency estimate.
    quote_role: REVIEW_SYNTHESIS
diagnosis:
- name: Skeletal survey and bone densitometry
  description: Radiographs characterize skull-vault and long-bone cortical thickening, while DXA quantifies density. The classic type I pattern differs from the skull-base, sandwich-vertebra and bone-within-bone pattern of type II, but clinical overlap and LRP6 phenocopies make molecular assessment useful. Normal DXA does not automatically exclude a reported cortical-overgrowth phenotype.
  evidence:
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Dual-energy X-ray absorptiometry (DEXA) scan revealed elevated bone mass.
    explanation: DEXA is the densitometric confirmation step used in the reported workup.
- name: LRP5 sequencing
  description: LRP5 analysis in the context of imaging and family history distinguishes molecularly supported LRP5 high bone mass from other sclerosing dysplasias. Testing should accommodate sequence variants and small in-frame changes rather than assuming every causal variant is a first-propeller missense substitution. A reported cytoplasmic association remains functionally unconfirmed.
  evidence:
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Genetic analysis and appropriate denomination of LRP5 HBM are fundamental for diagnosis and to mitigate the confusion that has long characterized this disease.
    explanation: States that molecular analysis is central to establishing this diagnosis.
    quote_role: REVIEW_SYNTHESIS
  - reference: PMID:29208525
    reference_title: 'Novel familial mutation of LRP5 causing high bone mass: Genetic analysis, clinical presentation, and characterization of bone matrix mineralization.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In both individuals, we detected a novel heterozygous duplication of six basepairs in the LRP5 gene, resulting in an insertion of two amino acids, very likely associated with a gain-of-function.
    explanation: Affected mother and daughter had a heterozygous in-frame duplication; the report proposes gain of function rather than measuring receptor activity.
- name: Bone turnover and circulating Wnt-inhibitor measurements
  description: Normal turnover markers do not exclude high bone mass. In 16 G171V/N198S carriers, 13 unaffected relatives and 24 unrelated controls, mean affected Z-score was 6.4 but CTX and P1NP did not differ significantly across groups. Sclerostin and DKK1 did not distinguish carriers from relatives. SFRP-4 was higher in both affected and unaffected relatives than unrelated controls, so it did not discriminate mutation status within those kindreds. These measurements are not validated confirmatory tests. A prior T253I study had different biomarker findings, limiting generalization across alleles.
  evidence:
  - reference: PMID:24927689
    reference_title: "Serum levels of sclerostin, Dickkopf-1, and secreted frizzled-related protein-4 are not changed in individuals with high bone mass causing mutations in LRP5."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: There were no differences in CTX or P1NP values among the three groups.
    explanation: Normal-group comparisons despite marked high bone mass; lack of significance is not universal equivalence.
  - reference: PMID:24927689
    reference_title: "Serum levels of sclerostin, Dickkopf-1, and secreted frizzled-related protein-4 are not changed in individuals with high bone mass causing mutations in LRP5."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: There was no group effect for sclerostin when analyzed by one-way ANOVA
    explanation: Direct measurement in the G171V/N198S kindred comparison.
  - reference: PMID:24927689
    reference_title: "Serum levels of sclerostin, Dickkopf-1, and secreted frizzled-related protein-4 are not changed in individuals with high bone mass causing mutations in LRP5."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: there was an overall group effect by one-way ANOVA. When an ANCOVA analysis was conducted for Dkk-1, controlling for age did not affect the results in any pair-wise comparisons among the three groups, all of which remained nonsignificant.
    explanation: DKK1 did not show significant pairwise differences despite a borderline overall group effect.
  - reference: PMID:24927689
    reference_title: "Serum levels of sclerostin, Dickkopf-1, and secreted frizzled-related protein-4 are not changed in individuals with high bone mass causing mutations in LRP5."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: When age was controlled for, the serum SFRP-4 values in both the affected and unaffected kindreds members remained significantly higher than the mean value in controls (p=0.01 for both comparisons).
    explanation: The full text reports elevated SFRP-4 versus unrelated controls in both family groups; the abstract should not be read as universally unchanged serum concentrations.
differential_diagnoses:
- name: Autosomal dominant osteopetrosis type II (Albers-Schonberg disease)
  description: CLCN7-related dominant osteopetrosis has a resorption defect, often with sandwich vertebrae, bone-within-bone changes and increased fracture susceptibility. Clinical variability means that absence of fractures alone does not exclude it.
  evidence:
  - reference: PMID:12054167
    reference_title: Localization of the gene causing autosomal dominant osteopetrosis type I to chromosome 11q12-13.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: ADOI is the only type of osteopetrosis not associated with an increased fracture rate.
    explanation: The fracture-rate contrast is the stated discriminator between ADO1 and the other osteopetroses.
- name: LRP6 high bone mass
  description: LRP6-related high bone mass can resemble LRP5 disease clinically. A negative LRP5 result prompts consideration of LRP6 and other sclerosing dysplasias; it does not establish an LRP6 diagnosis.
  evidence:
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: the detection of pathogenic mutations in the low-density lipoprotein receptor-related protein 6 (LRP6) gene in some patients with autosomal dominant HBM phenotype led to the description of a clinically identical disorder in 2019, called LRP6 HBM
    explanation: Establishes LRP6 HBM as a separate gene producing a clinically identical high-bone-mass disorder.
    quote_role: REVIEW_SYNTHESIS
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: when comparing the affected individuals with patients carrying LRP5 mutations, no feature was found to differentiate LRP6 HBM from LRP5 HBM
    explanation: States directly that no clinical feature separates the two, which is why this differential is resolvable only by sequencing.
    quote_role: REVIEW_SYNTHESIS
- name: Sclerosteosis and van Buchem disease
  description: Sclerosteosis and van Buchem disease reduce sclerostin activity through SOST coding or regulatory defects and can cause marked skeletal overgrowth. They involve the same antagonist–receptor pathway as LRP5 high bone mass, with different inheritance and molecular causes.
  evidence:
  - reference: PMID:18328982
    reference_title: Sclerosing bone disorders.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Other less common recessive or dominant sclerosing disorders, such as endosteal hyperostosis, sclerostosis, van Buchen disease and high bone mass syndrome, are due to mutations in two genes (LRP5 and SOST) of the Wnt pathway that induce increased osteoblast activity.
    explanation: Groups the SOST and LRP5 disorders as the same Wnt-axis differential.
    quote_role: REVIEW_SYNTHESIS
- name: Osteoporosis-pseudoglioma syndrome
  description: Recessive loss-of-function LRP5 disease causes osteoporosis-pseudoglioma syndrome, with low bone mass and ocular disease. It is an allelic contrast rather than a high-bone-mass clinical phenocopy.
  evidence:
  - reference: PMID:12579474
    reference_title: Six novel missense mutations in the LDL receptor-related protein 5 (LRP5) gene in different conditions with an increased bone density.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The LDL receptor-related protein 5 (LRP5) gene has been shown to be involved in both osteoporosis-pseudoglioma syndrome and the high-bone-mass phenotype and turned out to be an important regulator of peak bone mass in vertebrates.
    explanation: Establishes the allelic relationship between the low- and high-bone-mass LRP5 disorders.
animal_models:
- name: Lrp5 p.G171V knock-in mouse
  species: Mouse
  genotype: Homozygous Lrp5 p.G171V knock-in at the endogenous locus, crossed with SOST- or Dkk1-overexpressing transgenes
  publication: PMID:25808845
  description: The 2015 inhibitor-challenge study used homozygous G171V knock-in mice. Endogenous-locus expression preserves regulatory context but differs from the usual heterozygous human genotype. Skeletal responses depend on inhibitor, site and sex.
  modeled_mechanisms:
  - target: LRP5 Gain-of-Function Variation
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    model_scale: ORGANISM
    description: 'Carries the orthologous substitution at the endogenous locus, and reproduces the defining property of the human allele, resistance to sclerostin.

      '
    limitations: Two mutant alleles differ from human heterozygosity. Cranial-nerve morbidity was not evaluated, so absence of that phenotype cannot be inferred. Background differences and different transgene promoters/expression levels limit cross-inhibitor comparisons.
    readouts:
    - name: Bone response to osteocytic SOST overexpression
      target: LRP5 Gain-of-Function Variation
      direction: UNCHANGED
      interpretation: The main whole-body and selected bone endpoints did not show significant SOST-induced reductions in HBM mice, unlike controls. This is resistance in specified readouts, not proof of zero response in every microarchitectural parameter.
      evidence:
      - reference: PMID:25808845
        reference_title: High Bone Mass-Causing Mutant LRP5 Receptors Are Resistant to Endogenous Inhibitors In Vivo.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: We observed that the (8kb) Dmp1-SOST transgene significantly lowered whole-body bone mineral density (BMD), bone mineral content (BMC), femoral and vertebral trabecular bone volume fraction (BV/TV), and periosteal bone-formation rate (BFR) in wild-type mice but not in mice with Lrp5 p.G171V and p.A214V alleles.
        explanation: Abstract summary of specified endpoints; full text reports some residual architectural effects.
    evidence:
    - reference: PMID:25808845
      reference_title: High Bone Mass-Causing Mutant LRP5 Receptors Are Resistant to Endogenous Inhibitors In Vivo.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: We previously reported the creation of two Lrp5 HBM knock-in mouse models, in which the human p.A214V or p.G171V missense mutations were knocked into the endogenous Lrp5 locus.
      explanation: Establishes that these are knock-ins of the human disease alleles at the endogenous locus, which is what makes them informative for this node.
- name: Lrp5 p.A214V knock-in mouse
  species: Mouse
  genotype: Homozygous Lrp5 p.A214V knock-in at the endogenous locus, crossed with SOST- or Dkk1-overexpressing transgenes
  publication: PMID:25808845
  description: The 2015 inhibitor-challenge study used homozygous A214V knock-in mice. Endogenous-locus expression preserves regulatory context but differs from the usual heterozygous human genotype. Skeletal responses depend on inhibitor, site and sex.
  modeled_mechanisms:
  - target: LRP5 Gain-of-Function Variation
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    model_scale: ORGANISM
    description: Reproduces sclerostin resistance but remains more sensitive than G171V to DKK1. Under DKK1 challenge, A214V whole-body aBMD fell by approximately 11–14%, with site-specific effects.
    limitations: Two mutant alleles differ from human heterozygosity. Cranial-nerve morbidity was not evaluated, so absence of that phenotype cannot be inferred. Background differences and different transgene promoters/expression levels limit cross-inhibitor comparisons.
    evidence:
    - reference: PMID:25808845
      reference_title: High Bone Mass-Causing Mutant LRP5 Receptors Are Resistant to Endogenous Inhibitors In Vivo.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: The (2.3kb) Col1a1-Dkk1 transgene significantly lowered whole-body BMD, BMC, and vertebral BV/TV in wild-type mice and affected p.A214V mice more than p.G171V mice.
      explanation: Documents the allele-specific difference in DKK1 sensitivity that limits how far this model generalises.
- name: Conditional Lrp5 HBM with Wls deletion in late osteoblasts and osteocytes
  species: Mouse
  genotype: Dmp1-Cre activation of conditional G171V or A214V Lrp5 alleles with conditional Wls deletion
  publication: PMID:42113468
  description: Tests whether intracellular retention of G171V permits bone accrual when Wnt secretion is impaired. Severe Wls-associated osteopenia persisted with either HBM allele; some male bone-mineral-content endpoints showed partial effects.
  modeled_mechanisms:
  - target: Enhanced Canonical Wnt Signaling in Bone-Forming Cells
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    model_scale: ORGANISM
    description: Perturbation tests the dependence of HBM behavior on the ligand-secretion environment.
    limitations: Wls deletion can change resorption and intracellular ligand positioning; these confound a simple inference about receptor localization. This is an engineered compound genotype, not isolated human LRP5 disease.
    evidence:
    - reference: PMID:42113468
      reference_title: Different Lrp5-HBM mutations induce magnitude- and surface-selective effects that are not explained by receptor trafficking.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: Wls-deleted mice exhibited a severe low bone mass phenotype whether G171V or A214V was present or not.
      explanation: Conditional Dmp1-Cre experiments constrain a ligand-independent or intracellular-retention explanation; altered resorption and intracellular ligand localization remain potential confounders.
  evidence:
  - reference: PMID:42113468
    reference_title: Different Lrp5-HBM mutations induce magnitude- and surface-selective effects that are not explained by receptor trafficking.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: Wls-deleted mice exhibited a severe low bone mass phenotype whether G171V or A214V was present or not.
    explanation: Conditional Dmp1-Cre experiments constrain a ligand-independent or intracellular-retention explanation; altered resorption and intracellular ligand localization remain potential confounders.
discussions:
- discussion_id: ado1_osteoclast_link_mechanism
  kind: KNOWLEDGE_GAP
  prompt: Which signals explain reduced resorptive responses in T253I disease, and how far does this mechanism generalize to other LRP5 HBM alleles?
  attaches_to:
  - pathophysiology#Reduced Osteoclast Number and Resorptive Response
  rationale: Normal tested osteoclast endpoints under supplied RANKL/M-CSF favor environmental dependence but do not prove that the entire intrinsic program is unaffected. The T253I authors proposed altered osteoblastic support without demonstrating a mediator. A later study actually measured circulating RANKL/OPG in 16 affected G171V/N198S carriers, 13 unaffected relatives and unrelated controls; the ratio difference was nonsignificant (p=0.09). This neither proves nor excludes altered local signaling at remodeling surfaces, and does not directly resolve T253I biology. Allele-specific co-culture or in vivo perturbation studies are needed.
  evidence:
  - reference: PMID:24927689
    reference_title: Serum levels of sclerostin, Dickkopf-1, and secreted frizzled-related protein-4 are not changed in individuals with high bone mass causing mutations in LRP5.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: It is also of interest that the RANKL/OPG ratio was higher in the affected individuals than in the other two groups, although this too was not significant.
    explanation: The ratio was measured, with p=0.09 in Table 1; serum measurements are not a test of local osteoblast–osteoclast mediation.
- discussion_id: ado1_neuro_ascertainment_bias
  kind: KNOWLEDGE_GAP
  prompt: Does the 19.4% neurological involvement figure reflect the true rate, or ascertainment bias in a literature assembled from case reports?
  attaches_to:
  - pathophysiology#Cranial Foramina Narrowing
  rationale: 'The figure comes from pooling published cases across a century of shifting nomenclature, and symptomatic patients are far more likely to be published than the asymptomatic carriers found incidentally on DEXA. The review itself notes that neurological manifestations were previously considered absent, which shows how much the estimate has moved with ascertainment. A population-based or family-based series would be needed to fix the rate.

    '
- discussion_id: ado1_g171v_trafficking
  kind: KNOWLEDGE_GAP
  prompt: How does G171V enhance bone accrual despite reduced surface localization in some experimental systems?
  attaches_to:
  - pathophysiology#Enhanced Canonical Wnt Signaling in Bone-Forming Cells
  rationale: Earlier cellular work proposed preserved autocrine signaling with reduced extracellular inhibitor access. The 2026 Wls-deletion experiments did not support preferential rescue by intracellularly retained G171V, but altered resorption and intracellular ligand positioning limit exclusion of every trafficking mechanism. Relative contributions of antagonist resistance, receptor localization and ligand availability remain unresolved.
  evidence:
  - reference: PMID:42113468
    reference_title: Different Lrp5-HBM mutations induce magnitude- and surface-selective effects that are not explained by receptor trafficking.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: Wls-deleted mice exhibited a severe low bone mass phenotype whether G171V or A214V was present or not.
    explanation: Conditional Dmp1-Cre experiments constrain a ligand-independent or intracellular-retention explanation; altered resorption and intracellular ligand localization remain potential confounders.
treatments:
- name: Clinical surveillance
  description: Management is individualized to skeletal and neurologic symptoms. Hearing, cranial nerve deficits and signs of intracranial hypertension warrant clinical assessment. The cited case literature does not establish a standard surveillance interval or a disease-modifying treatment.
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  notes: Reported interventions address symptoms or compression. Treatments used for other osteopetrosis mechanisms should not be inferred to benefit LRP5 high bone mass.
  evidence:
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: In summary, neurological involvement may occur because of nerve tissue compression by hyperostotic bone, cerebellar disturbances due to a reduction in size of the posterior cranial fossa or tonsillar herniation, and chronic intracranial hypertension
    explanation: Distinguishes direct nerve compression from reduced posterior-fossa space and pressure-related complications.
    quote_role: REVIEW_SYNTHESIS
- name: Hearing rehabilitation
  description: External hearing aids were used for mixed deafness in the A242T index case. This observation supports individualized hearing rehabilitation without establishing comparative efficacy.
  evidence:
  - reference: PMID:37659026
    reference_title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: At age 35, external hearing aids were placed due to complete, bilateral, and mixed hearing loss caused by the narrowing of internal and external acoustic meati.
    explanation: Index A242T case with anatomically described auditory canal narrowing.
  treatment_term:
    preferred_term: Hearing rehabilitation
    term:
      id: NCIT:C15315
      label: Rehabilitation
  therapeutic_modality: DEVICE
- name: Specialist surgical decompression
  description: Occipital decompression has been reported in an LRP5 insertion-allele carrier with foramen magnum stenosis. A separate clinically diagnosed, genetically untested ADO1 case had temporary relief after posterior fossa decompression and prolonged relief after microvascular decompression for recurrent trigeminal neuralgia. These selected cases support evaluation of documented compressive complications, not routine prophylactic surgery or disease modification.
  evidence:
  - reference: PMID:29208525
    reference_title: 'Novel familial mutation of LRP5 causing high bone mass: Genetic analysis, clinical presentation, and characterization of bone matrix mineralization.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: When the daughter had part of the occipital bone surgically removed, the bone sample was used for the visualization of bone lamellar structure and bone cells as well as the measurement of bone mineralization density distribution (BMDD).
    explanation: Confirms surgery in a genetically characterized case without supplying a controlled efficacy estimate.
  - reference: PMID:41431003
    reference_title: 'Staged posterior fossa decompression and microvascular decompression for trigeminal neuralgia in autosomal dominant osteopetrosis type I: A case report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Throughout more than 5 years of follow-up, she remained entirely pain-free, without recurrence, and had discontinued all medications.
    explanation: Outcome after second-stage microvascular decompression in one clinically diagnosed ADO1 case; genetic testing was not performed.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: Specialist surgical decompression
    term:
      id: NCIT:C15329
      label: Surgical Procedure
- name: Mandibular reduction surgery
  description: A young woman diagnosed with Worth syndrome underwent mandibular reduction using cutting guides. This is a single reported surgical outcome for mandibular enlargement; the available abstract does not establish her genotype or comparative efficacy.
  therapeutic_modality: SURGERY
  evidence:
  - reference: PMID:36907844
    reference_title: Worth Syndrome-Patient Report, Diagnostic Work-Up, and Surgical Management of a Rare Craniofacial Entity.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The authors report the preoperative considerations in a young female with Worth syndrome, operative planning, and successful mandibular reduction using cutting guides.
    explanation: Primary surgical case using the historical Worth designation; limited to the available abstract.
  treatment_term:
    preferred_term: Mandibular reduction surgery
    term:
      id: NCIT:C15329
      label: Surgical Procedure
- name: Cochlear implantation
  description: A molecularly characterized insertion-allele carrier with congenital hearing impairment underwent cochlear implantation. The available abstract does not quantify hearing benefit.
  therapeutic_modality: DEVICE
  treatment_term:
    preferred_term: cochlear device implantation
    term:
      id: NCIT:C15329
      label: Surgical Procedure
    qualifiers:
    - predicate:
        preferred_term: medical device
        term:
          id: NCIT:C16830
          label: Medical Device
      value:
        preferred_term: cochlear implant
        term:
          id: NCIT:C157820
          label: Cochlear Implant
  evidence:
  - reference: PMID:29208525
    reference_title: 'Novel familial mutation of LRP5 causing high bone mass: Genetic analysis, clinical presentation, and characterization of bone matrix mineralization.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: the daughter suffered from congenital hearing impairment resulting in cochlear implantation, recurrent facial palsy, and migraine
    explanation: Primary report of hearing rehabilitation in a molecularly characterized family.
notes: 'This entry retains MONDO:0011877 while covering the overlapping LRP5 high-bone-mass, Worth-type endosteal-hyperostosis and historical ADO1 literature. Modern usage distinguishes this primarily Wnt-related bone-accrual disorder from classical osteoclast-resorption defects; T253I data nevertheless show that resorptive responses can contribute.

  The 5.5/100,000 estimate in PMID:3829443 describes a historical Funen osteopetrosis cohort containing 33 patients, including one non-dominant case. Its untyped carriers and asymptomatic fraction do not supply LRP5-specific prevalence or penetrance, so those structured estimates have been removed. The 155-case historical review includes only 64 genetically tested patients, and each clinical percentage uses its own available-data denominator.

  No disease-specific GeneReviews chapter was identified. CLCN7-Related Osteopetrosis (PMID:20301306) and TCIRG1-Related Osteopetrosis (PMID:40875877) concern different diseases and are not transferred as care guidelines for LRP5 HBM. Lrp5 loss-of-function models alone represent the opposite skeletal mechanism.'
references:
- reference: PMID:12054167
  title: Localization of the gene causing autosomal dominant osteopetrosis type I to chromosome 11q12-13.
- reference: PMID:12579474
  title: Six novel missense mutations in the LDL receptor-related protein 5 (LRP5) gene in different conditions with an increased bone density.
- reference: PMID:16251418
  title: Osteoclasts from patients with autosomal dominant osteopetrosis type I caused by a T253I mutation in low-density lipoprotein receptor-related protein 5 are normal in vitro, but have decreased resorption capacity in vivo.
- reference: PMID:17052975
  title: LRP5 mutations linked to high bone mass diseases cause reduced LRP5 binding and inhibition by SOST.
- reference: PMID:18328982
  title: Sclerosing bone disorders.
- reference: PMID:20855225
  title: 'Genetics of bone diseases: Paget''s disease, fibrous dysplasia, osteopetrosis, and osteogenesis imperfecta.'
- reference: PMID:24927689
  title: Serum levels of sclerostin, Dickkopf-1, and secreted frizzled-related protein-4 are not changed in individuals with high bone mass causing mutations in LRP5.
- reference: PMID:25808845
  title: High Bone Mass-Causing Mutant LRP5 Receptors Are Resistant to Endogenous Inhibitors In Vivo.
- reference: PMID:29208525
  title: 'Novel familial mutation of LRP5 causing high bone mass: Genetic analysis, clinical presentation, and characterization of bone matrix mineralization.'
- reference: PMID:36971833
  title: 'Novel mutation in LRP5 gene cause rare osteosclerosis: cases studies and literature review.'
- reference: PMID:37659026
  title: 'LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.'
- reference: PMID:41431003
  title: 'Staged posterior fossa decompression and microvascular decompression for trigeminal neuralgia in autosomal dominant osteopetrosis type I: A case report.'
- reference: PMID:42113468
  title: Different Lrp5-HBM mutations induce magnitude- and surface-selective effects that are not explained by receptor trafficking.
- reference: PMID:36907844
  title: Worth Syndrome-Patient Report, Diagnostic Work-Up, and Surgical Management of a Rare Craniofacial Entity.
progression:
- phase: Variable onset and adult course
  notes: 'Clinical timing varies: congenital hearing impairment is documented in an insertion-allele carrier, while adult bone mass need not increase continuously. The 8–76-year symptom-onset range in the historical Funen survey is not a molecularly defined LRP5 estimate and is not transferred here. Cross-sectional age associations do not establish individual longitudinal BMD trajectories.'
  evidence:
  - reference: PMID:29208525
    reference_title: 'Novel familial mutation of LRP5 causing high bone mass: Genetic analysis, clinical presentation, and characterization of bone matrix mineralization.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: the daughter suffered from congenital hearing impairment resulting in cochlear implantation, recurrent facial palsy, and migraine
    explanation: Congenital hearing impairment documents early onset in a molecularly characterized insertion-allele carrier.
  - reference: PMID:24927689
    reference_title: "Serum levels of sclerostin, Dickkopf-1, and secreted frizzled-related protein-4 are not changed in individuals with high bone mass causing mutations in LRP5."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: individuals with HBM mutations in LRP5 do not generally show progressive increases in bone mass as adults.
    explanation: Clinical context cited in the biomarker paper discussion; not a longitudinal measurement from its cross-sectional study.
    quote_role: BACKGROUND

📚

References & Deep Research

References

14

PMID:12054167

Localization of the gene causing autosomal dominant osteopetrosis type I to chromosome 11q12-13.

No top-level findings curated for this source.

PMID:12579474

Six novel missense mutations in the LDL receptor-related protein 5 (LRP5) gene in different conditions with an increased bone density.

No top-level findings curated for this source.

PMID:16251418

Osteoclasts from patients with autosomal dominant osteopetrosis type I caused by a T253I mutation in low-density lipoprotein receptor-related protein 5 are normal in vitro, but have decreased resorption capacity in vivo.

No top-level findings curated for this source.

PMID:17052975

LRP5 mutations linked to high bone mass diseases cause reduced LRP5 binding and inhibition by SOST.

No top-level findings curated for this source.

PMID:18328982

Sclerosing bone disorders.

No top-level findings curated for this source.

PMID:20855225

Genetics of bone diseases: Paget's disease, fibrous dysplasia, osteopetrosis, and osteogenesis imperfecta.

No top-level findings curated for this source.

PMID:24927689

Serum levels of sclerostin, Dickkopf-1, and secreted frizzled-related protein-4 are not changed in individuals with high bone mass causing mutations in LRP5.

No top-level findings curated for this source.

PMID:25808845

High Bone Mass-Causing Mutant LRP5 Receptors Are Resistant to Endogenous Inhibitors In Vivo.

No top-level findings curated for this source.

PMID:29208525

Novel familial mutation of LRP5 causing high bone mass: Genetic analysis, clinical presentation, and characterization of bone matrix mineralization.

No top-level findings curated for this source.

PMID:36971833

Novel mutation in LRP5 gene cause rare osteosclerosis: cases studies and literature review.

No top-level findings curated for this source.

PMID:37659026

LRP5 high bone mass (Worth-type autosomal dominant endosteal hyperostosis): case report and historical review of the literature.

No top-level findings curated for this source.

PMID:41431003

Staged posterior fossa decompression and microvascular decompression for trigeminal neuralgia in autosomal dominant osteopetrosis type I: A case report.

No top-level findings curated for this source.

PMID:42113468

Different Lrp5-HBM mutations induce magnitude- and surface-selective effects that are not explained by receptor trafficking.

No top-level findings curated for this source.

PMID:36907844

Worth Syndrome-Patient Report, Diagnostic Work-Up, and Surgical Management of a Rare Craniofacial Entity.

No top-level findings curated for this source.

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 (1)

Create: Autosomal Dominant Osteopetrosis Type I (MONDO:0011877) · 2026-09-06T16:07:19Z · View source

De novo curation of ADO1 / LRP5 high bone mass. Lump/split: curated as a DISEASE rather than a has_subtypes row on Osteopetrosis. ADO1 is mechanistically the inverse of the other osteopetroses (osteoblastic bone formation excess via LRP5 gain of function, not osteoclastic resorption failure), and the literature formally reclassified it out of the osteopetrosis group into the high-bone-mass diseases (PMID:20855225). Autosomal_Dominant_Osteopetrosis_Type_II and Autosomal_Recessive_Osteopetrosis already exist as separate entries, so a separate ADO1 entry matches the established shape. No kb entry carried hgnc:6697 for a bone phenotype before this one. Pathograph: LRP5 first-beta-propeller substitution -> constitutive canonical Wnt signalling in osteoblasts -> increased osteoblastic formation and (indirectly) reduced osteoclast number -> generalized osteosclerosis -> cranial foramina narrowing -> hearing loss, headache, anosmia. The osteoblast-to-osteoclast edge is recorded INDIRECT_KNOWN_INTERMEDIATES with directness: INDIRECT because the only source states it as an explicit speculation. Notable negative: 'Absence of increased fracture rate' is curated as a phenotype with frequency EXCLUDED. It is the discriminating feature against ADO2 and is a positive claim about this disease rather than missing data. Deep research: one openscientist report (research/Autosomal_Dominant_Osteopetrosis_Type_I-deep-research-openscientist.md), 30/30 references resolved, 13/13 quoted claims verified, 0 unresolved terms. preflight-dr PASS on identity (LRP5 x42, OMIM 607634 matches MONDO). Its 'rival gene HBM' warning is a false positive: HBM is the high-bone-mass abbreviation, not a rival gene. Two report leads changed the entry. It surfaced Lrp5 p.G171V and p.A214V knock-in mice (PMID:25808845), which falsified a claim in an earlier draft of notes that no ADO1 model existed; two animal_models with modeled_mechanisms were added and the note corrected. It also surfaced a 5.5/100,000 population prevalence (PMID:3829443) which the report presented as an ADO-I figure. That attribution was NOT followed: the 1986 Funen County survey predates both the type I/II split and the LRP5 discovery, so its dominant-osteopetrosis cohort is mostly what is now ADO2. The figure is recorded as an explicit upper bound with that caveat. Validation: just validate passes schema plus 46/46 snippets verified against cached references; validate-terms, check-entity-refs, check-causal-targets, check-duplicate-keys, check-enum-values all pass. Note for tooling: CLAUDE.md documents a Prevalence slot rate_denominator that does not exist in src/dismech/schema/dismech.yaml; using it as documented fails schema validation.

OpenScientist ▸

Key Findings

openscientist-autonomous 30 citations 2026-09-06T16:02:27.296616

Key Findings

Finding 1 — ADO-I is an LRP5 gain-of-function high-bone-mass disorder (11q13) [human clinical]

Linkage analysis in two Danish ADO-I families mapped the disease locus to chromosome 11q12–13 (summated maximum LOD +6.54 with marker D11S1889; candidate region 6.6 cM between D11S1765 and D11S4113), the interval containing LRP5 (PMID: 12054167). Van Wesenbeeck and colleagues then identified six novel heterozygous missense mutations — D111Y, G171R, A214T, A214V, A242T, and T253I — in the N-terminal region of LRP5 across a spectrum of increased-bone-density conditions including osteopetrosis type I. All cluster in the same region as the previously reported G171V HBM mutation; the mutations are "located in the aminoterminal part of the gene" before the first EGF-like/β-propeller domain (PMID: 12579474). The recognition of these gain-of-function alleles prompted a formal reclassification: "The identification of LRP5 gain-of-function mutations in autosomal dominant osteopetrosis type I prompted a revision of the classification scheme, and this form is now being included among the high-bone-mass diseases" (PMID: 20855225).

This is the central reframing of the disease: ADO-I is not a defect of bone removal but of excessive bone formation driven by a Wnt co-receptor.

Finding 2 — Mechanism: mutant LRP5 resists sclerostin/DKK1, causing constitutive Wnt/β-catenin signaling [in vitro + mouse]

The gain-of-function is a loss of inhibition. In vitro, six different HBM-LRP5 mutants are resistant: "neither Dickkopf1 (DKK1) nor sclerostin efficiently inhibits HBM-LRP5 signaling" (PMID: 18521528); DKK1 and sclerostin act as independent regulators of LRP5, and both are impaired by the HBM mutations. This receptor-resistance model was confirmed in vivo with knock-in mice: "the (8kb) Dmp1-SOST transgene significantly lowered whole-body bone mineral density (BMD), bone mineral content (BMC), femoral and vertebral trabecular bone volume fraction (BV/TV), and periosteal bone-formation rate (BFR) in wild-type mice but not in mice with Lrp5 p.G171V and p.A214V alleles" (PMID: 25808845). The p.A214V allele was more sensitive to DKK1 than p.G171V, indicating mutation-specific, differential inhibitor sensitivity.

Critically, the osteoclast is a bystander. Osteoclasts from a T253I ADO-I patient showed "normal osteoclastogenesis, expression of osteoclast markers, morphology, and localization of proteins involved in bone resorption, such as ClC-7 and cathepsin K. The ability to resorb bone was also normal" in vitro, though they showed decreased resorption and low osteoclast numbers in vivo — consistent with an osteoblast-driven defect that secondarily reduces osteoclastogenic support (PMID: 16251418). Circulating levels of the inhibitors themselves are normal — "There were no significant differences found in the serum levels of sclerostin (SOST), Dickkopf-1 (Dkk-1), or secreted frizzled-related protein-4 (SFRP-4) in affected vs. unaffected individuals" (PMID: 24927689) — confirming the lesion is at the receptor, not in ligand abundance.

Finding 3 — Clinical phenotype: generalized osteosclerosis maximal at the cranial vault, often asymptomatic, uniquely NOT fracture-prone [human clinical]

ADO-I "is characterized by a generalized osteosclerosis, most pronounced at the cranial vault"; patients "are often asymptomatic but some suffer from pain and hearing loss," and — the pathognomonic clinical fact — "ADOI is the only type of osteopetrosis not associated with an increased fracture rate" (PMID: 12054167). Across the overlapping LRP5-HBM/Worth-type endosteal-hyperostosis spectrum (155 reported patients), "Neurological involvement and increased serum alkaline phosphatase (ALP) were present in 19.4% and 3.7% of cases, respectively. Facial changes and torus palatinus were observed in 61% and 41% of cases, respectively" (PMID: 37659026).

The contrast with ADO Type II (Albers-Schönberg disease, caused by CLCN7) is diagnostic: there, "Fractures were common (78% of patients) and healed slowly," with sandwich vertebrae and frequent orthopedic surgery (PMID: 10617161). The Wnt-built ADO-I bone is stronger, not more brittle.

Finding 4 — Markedly increased, age-progressive, cortical-predominant BMD; skull-vault thickening is the defining radiographic feature [human clinical]

Bollerslev and Andersen's original classification of 34 patients showed "Type I showed a pronounced sclerosis of the skull with an enlarged thickness of the cranial wall"; radiogrammetry demonstrated normal subperiosteal width but significantly enlarged cortical thickness (P<0.01) with a reduced medullary cavity, and serum acid phosphatase — a resorption marker — was markedly increased in Type II but not Type I (P<0.01) (PMID: 3377922). DXA of the entire skeleton quantified the magnitude: "Median BMD was markedly increased in the axial skeleton by 51% (44-56) and 42% (33-56), (median differences with 95% CI), respectively, for types I and II compared to normal controls," with no overlap between patient and control ranges and a positive age–BMD correlation in ADO but not controls, indicating progressive osteosclerosis with aging (PMID: 7605703).

Finding 5 — Epidemiology & inheritance: AD, incompletely penetrant, variably expressed; prevalence ≈5.5/100,000 [human clinical]

The Danish Funen County ascertainment gives the best population estimate: "the prevalence was 5.5/100,000 inhabitants. The study disclosed 33 patients of whom 32 had the mild, autosomal dominant form of osteopetrosis. Two obligate carriers, who had the genotype but were not phenotypically affected" — direct evidence of incomplete penetrance (PMID: 3829443). Expressivity is wide and age-dependent: "39% were asymptomatic. The age of first appearance of symptoms also varied widely (8-76 years), with a tendency to increasing symptoms with aging. The frequency of fractures was low" (PMID: 3829443). Transmission is autosomal dominant through heterozygous LRP5 gain-of-function variants (PMID: 12579474); each child of an affected parent has a 50% chance of inheriting the allele, though penetrance is not guaranteed.

Finding 6 — Mouse models: HBM knock-ins reproduce strong bone; Lrp5-knockout does the opposite [mouse]

The genetic direction of effect is mirrored in mice. Transgenic mice carrying human LRP5 G171V "show a similar phenotype with greater bone mass and biomechanical performance than wild-type mice," and nano-indentation showed "The intrinsic material property that reflected the bone modulus was greater (48%) in the HBM as compared to the NTG mice" — the material basis of fracture resistance (PMID: 20503060). The A214V knock-in is "a high bone mass (HBM) mouse (Lrp5(+/p.A214V)) that has increased bone strength from enhanced Wnt signaling," and crossing it into an osteogenesis-imperfecta model raised bone mass and strength (PMID: 27297606). Conversely, Lrp5-knockout mice have low femoral-neck cross-sectional area and BV/TV, opposite to Sost-knockout (PMID: 31437568). Newer transgenic A241T mice (the human A242T equivalent) reproduce the HBM phenotype (PMID: 38909879) and even enhance dental-implant osseointegration (PMID: 41025443).

Finding 7 — Principal morbidity is cranial-nerve compression from skull-base hyperostosis, not fracture [human clinical]

Because bone accrues maximally at the skull, ADO-I morbidity is neuro-compressive. A 26-year-old woman with ADO-I "presented with intractable, electric shock-like facial pain consistent with" trigeminal neuralgia from neurovascular compression compounded by cranial hyperostosis; the report notes "This condition may lead to cranial nerve compression syndromes, with trigeminal neuralgia (TN) occurring infrequently." She was treated durably by staged suboccipital craniectomy/C1 laminectomy plus microvascular decompression, with 5-year sustained relief (PMID: 41431003). More broadly in adult osteopetrosis, "Bone marrow failure, dental abscess, deafness and visual loss are often underestimated and neglected in relation with lack of awareness and expertise" (PMID: 38593953). Because most patients are asymptomatic, the disorder is frequently found incidentally (PMID: 3829443).

Finding 8 — Structural basis: mutations map to the E1 β-propeller, the sclerostin/DKK1 docking module [structural/computational]

The crystal structure of the LRP6 E1 β-propeller revealed it to be a peptide-recognition module: "human missense mutations that result in bone overgrowth (bone mineral density, or BMD, mutations) cluster to the E1 propeller domain of LRP5," and "the consensus E1 binding sequence is a close match to a conserved tripeptide motif present in all Wnt inhibitors that bind LRP5/6. We show that this motif is important for DKK1 and SOST binding to LRP6 and for inhibitory function, providing a detailed structural explanation for the effect of the BMD mutations" (PMID: 21944579). This is the mechanistic keystone: all ADO-I mutations (G171V, D111Y, G171R, A214T/V, A242T, T253I) sit in the exact surface where the inhibitors' NxI tripeptide motif must dock, so the mutant receptor cannot be silenced (PMID: 12579474, PMID: 18521528).

Finding 9 — Diagnosis is radiologic + LRP5 sequencing, with low/normal bone-turnover chemistry [human clinical]

"The diagnosis is radiologic, supported by biochemical and genetic examination to identify mutations in the key genes involved in osteoclasts, TCIRG1, CLCN7, OSTM1, SNX10, RANK, and RANKL" — and, for the HBM/Type I form, LRP5 (PMID: 42096006). Radiographs/CT show generalized osteosclerosis maximal at the cranial vault with cortical thickening and reduced medullary cavity (PMID: 3377922); DXA shows markedly elevated BMD with no overlap with controls (PMID: 7605703). Biochemistry shows normal/low serum acid phosphatase (elevated in Type II), consistent with low turnover (PMID: 3377922, PMID: 3829443). Circulating SOST/DKK1/SFRP-4 are normal and are not diagnostic biomarkers (PMID: 24927689). Radiologists play a key role and must anticipate subtype-specific complications (PMID: 38483591).

Finding 10 — Management is supportive/surgical; the mechanism validates anti-sclerostin/anti-DKK1 osteoporosis drugs [human clinical + mouse]

There is no curative drug. "Treatment is at present largely the management of complications and includes vitamin D and calcium supplements, IFN-γ therapy, and hematopoietic stem cell transplantation (HSCT), the latter being the treatment of choice for most forms of osteopetrosis" — but HSCT targets the osteoclast-defect (recessive) forms and is mechanistically inapplicable to LRP5-driven ADO-I (PMID: 42096006). Symptomatic cranial-nerve compression is managed surgically with durable benefit — "A staged decompressive approach represents an effective and durable treatment option" (PMID: 41431003). The ADO-I mechanism is the therapeutic converse of anabolic osteoporosis therapy: "combined administration of sclerostin and Dkk1 antibody in WT mice produced a synergistic effect on bone gain" (PMID: 29875318) — the very biology that ADO-I patients embody constitutively. Prevention is limited to genetic counseling and cascade testing/surveillance (PMID: 3829443).

Full Section-by-Section Report

1. Disease Information

ADO-I is a rare, mild, autosomal-dominant sclerosing bone dysplasia characterized by generalized osteosclerosis most pronounced at the cranial vault, elevated bone mineral density that increases with age, and — uniquely among the osteopetroses — no increased fracture rate. It is now classified as a high-bone-mass (HBM) disorder driven by LRP5 Wnt-co-receptor gain of function rather than as an osteoclast-resorption defect.

Resource	Identifier
OMIM	#607634 (Osteopetrosis, autosomal dominant 1)
Orphanet	ORPHA:53 (Osteopetrosis, autosomal dominant)
MeSH	D010022 (Osteopetrosis)
ICD-10	Q78.2 (Osteopetrosis)
ICD-11	FB80.20 (Osteopetrosis)
Gene	LRP5 (HGNC:6697), 11q13

Synonyms / related terms: Osteopetrosis autosomal dominant type 1; ADO-I; LRP5-related high bone mass; Worth-type autosomal dominant endosteal hyperostosis (overlapping spectrum); "benign osteopetrosis" (a partly misleading label, since cranial complications can be serious).

Source of information: Primarily aggregated disease-level resources (OMIM, Orphanet) plus published family and cohort studies; the strongest epidemiologic data derive from a systematic Danish population ascertainment (PMID: 3829443).

2. Etiology

Causal factor — genetic: Heterozygous gain-of-function missense mutations in LRP5. Reported alleles include G171V (the archetypal HBM mutation), D111Y, G171R, A214T, A214V, A242T, and T253I (PMID: 12579474). All localize to the N-terminal first β-propeller (E1) domain (PMID: 21944579).

Genetic risk factors: The causal variant itself is the risk factor; a single heterozygous E1-domain allele is sufficient. No independent susceptibility loci are established. Modifier effects on magnitude and skeletal-surface selectivity differ between alleles (e.g., G171V vs A214V), but combining two HBM alleles does not exceed either alone (PMID: 42113468).

Environmental risk factors: None causally established. Age is a strong modifier of expression — BMD and symptoms increase with age (PMID: 7605703, PMID: 3829443).

Protective factors: Not applicable in the conventional sense. Notably, the mutation itself is "protective" against fracture and osteoporosis — the same biology exploited pharmacologically by anti-sclerostin drugs.

Gene–environment interactions: In Lrp5^A214V mice, the HBM genotype altered the vitamin D endocrine system to maintain high bone mass even under dietary calcium restriction, showing genotype-driven reshaping of calcium handling (PMID: 38477773). This is model-organism evidence of a GxE interaction on peak bone mass.

3. Phenotypes

Phenotype	Type	Onset / Course	Frequency	Suggested HPO
Generalized osteosclerosis, maximal cranial vault	Radiographic/physical	Childhood–adult, progressive with age	Defining feature	HP:0011001 (Increased bone mineral density); HP:0002684 (Thickened calvaria)
Increased bone mineral density	Lab/imaging	Age-progressive	Universal (no overlap with controls)	HP:0011001
Asymptomatic status	—	—	~39% of carriers	—
Hearing loss / deafness	Clinical sign	Adult	Subset (cranial-nerve)	HP:0000365 (Hearing impairment)
Cranial-nerve palsy / facial pain (trigeminal neuralgia)	Symptom	Adult	Uncommon but serious	HP:0100259 (Cranial nerve compression); HP:0010829 (Abnormal trigeminal nerve)
Visual compromise / optic involvement	Clinical sign	Adult	Uncommon	HP:0000505 (Visual impairment)
Facial changes / torus palatinus	Physical	Adult	61% / 41% (HBM spectrum)	HP:0001999 (Abnormal facial shape)
Bone pain	Symptom	Variable	Subset	HP:0002653 (Bone pain)
Low fracture frequency	—	—	Low; NOT increased	(absence of HP:0002659)

Severity/progression: Mild, chronic, progressive osteosclerosis; highly variable expressivity with wide age of first symptom (8–76 years) (PMID: 3829443). Quality-of-life impact: Often negligible (asymptomatic majority); when cranial-nerve compression occurs, impact can be significant (chronic pain, deafness, visual loss) but is frequently amenable to surgery (PMID: 41431003, PMID: 38593953).

4. Genetic / Molecular Information

Causal gene: LRP5 (low-density-lipoprotein-receptor-related protein 5), HGNC:6697, OMIM 603506, chromosome 11q13. Pathogenic variants: Heterozygous missense — G171V, D111Y, G171R, A214T, A214V, A242T, T253I — all in the E1 β-propeller (PMID: 12579474). Classification: pathogenic/likely-pathogenic under ACMG (well-established functional gain-of-function, cosegregation, absence in controls). Variant type: missense/single-nucleotide. Allele frequency: extremely rare/absent in gnomAD (private/family-specific). Origin: germline. Functional consequence:* gain of function via loss of inhibitor (SOST/DKK1) binding at E1 (PMID: 18521528, PMID: 21944579).

The loss-of-function pole of the same gene causes osteoporosis-pseudoglioma syndrome (OPPG) — a low-bone-mass phenotype — establishing LRP5 as a bidirectional bone-mass rheostat (PMID: 40940800). In silico analysis of 17 LRP5 nsSNPs found the gain-vs-loss outcome is "primarily dictated by the interaction between the molecule and LRP5, rather than the specific amino acid substitution" (PMID: 40255261).

Modifier genes: allele identity modifies magnitude/surface selectivity (PMID: 42113468). Epigenetic/chromosomal abnormalities: none established. Suggested annotations: LRP5 (HGNC:6697); Wnt-activated receptor activity (GO:0042813).

5. Environmental Information

No environmental toxin, radiation, lifestyle, or infectious agent causes ADO-I; it is a monogenic disorder. The only environmental interaction documented is dietary calcium: HBM-genotype mice maintain high bone mass under calcium restriction by altering vitamin D metabolism (PMID: 38477773). Infectious agents: not applicable.

6. Mechanism / Pathophysiology

Ordered causal chain (initiating lesion → clinical manifestation):

A heterozygous missense mutation in the E1 β-propeller of LRP5 (e.g., G171V) alters the surface where Wnt-inhibitor peptides dock (PMID: 12579474, PMID: 21944579).
This prevents sclerostin (SOST) and DKK1 from binding and inhibiting the receptor (PMID: 18521528; confirmed in vivo, PMID: 25808845).
Loss of inhibition results in constitutive Wnt/β-catenin signaling in osteoblast-lineage cells (β-catenin stabilization → nuclear translocation → RUNX2/Osterix activation) (PMID: 17395698, PMID: 39447984).
Sustained signaling leads to increased osteoblast proliferation, differentiation, and bone-formation rate (PMID: 25808845).
This produces generalized, age-progressive, cortical-predominant osteosclerosis with increased intrinsic material modulus — hence strong, fracture-resistant bone (PMID: 3377922, PMID: 7605703, PMID: 20503060).
Branch (osteoclast): osteoblast-derived signals secondarily reduce osteoclast support in vivo, though osteoclasts are intrinsically normal (inferred from patient-cell studies) (PMID: 16251418).
Bone accrual is maximal at the skull vault and base, which causes narrowing of cranial foramina and posterior-fossa crowding (PMID: 12054167).
This leads to cranial-nerve compression — hearing loss, trigeminal neuralgia, facial palsy, visual compromise — the principal source of morbidity (PMID: 41431003, PMID: 38593953).

Pathway/process detail: Canonical Wnt/β-catenin (KEGG hsa04310; Reactome Wnt signaling). Cellular processes: osteoblast differentiation (GO:0001649), positive regulation of bone mineralization (GO:0030501), Wnt signaling pathway (GO:0016055), positive regulation of osteoblast differentiation (GO:0045669). Protein dysfunction: gain of function via impaired inhibitor docking (not misfolding/aggregation). Cell types: osteoblasts (CL:0000062), osteocytes (CL:0000137, the SOST source), osteoclasts (CL:0000092, bystander). Subcellular: plasma-membrane receptor (GO:0005886); intriguingly the G171V receptor has poor membrane localization yet still causes HBM, so intracellular retention is unlikely to be the operative mechanism (PMID: 42113468).

LRP5 E1 mutation ──► SOST/DKK1 cannot dock ──► constitutive Wnt/β-catenin
│                                             │
│                                             ▼
│                                 ↑ osteoblast bone formation
│                                             │
▼                                             ▼
 (osteoclasts normal) ◄── ↓ secondary support   cortical-predominant osteosclerosis
                                       │
                                       ▼
                        skull-vault / base hyperostosis
                                       │
                                       ▼
                      cranial-nerve compression (morbidity)

7. Anatomical Structures Affected

Organ/system level: Skeletal system (primary). Cranial vault and skull base most severely affected (UBERON:0001474 bone element; UBERON:0004339 cranial skeletal system). Secondary: cranial nerves (nervous system) via compression; auditory apparatus (hearing loss); optic pathway (visual compromise); dental structures (torus palatinus).
Tissue/cell level: Cortical bone predominantly (thickened cortex, reduced medullary cavity, PMID: 3377922); osteoblasts (CL:0000062) are the driver cell; osteocytes (CL:0000137) as inhibitor source; osteoclasts (CL:0000092) intrinsically normal.
Subcellular: LRP5 at the plasma membrane (GO:0005886); β-catenin nuclear signaling (GO:0005634 nucleus).
Localization/laterality: Bilateral, symmetric, generalized osteosclerosis, cranially accentuated.

8. Temporal Development

Onset: Variable — childhood through adulthood; the classic AD form often becomes radiographically apparent in adolescence/early adulthood but ranges from 8 to 76 years for first symptoms (PMID: 3829443, PMID: 38483591). Onset pattern is insidious/chronic.
Progression: Slowly progressive; BMD rises with age (positive age–BMD correlation absent in controls) (PMID: 7605703). Course is stable-to-progressive, lifelong, not relapsing-remitting. No spontaneous remission.
Critical periods: Peak-bone-mass accrual during growth is amplified by the genotype (PMID: 38477773); surgical intervention windows arise when cranial-nerve compression becomes symptomatic.

9. Inheritance and Population

Epidemiology: Prevalence of the mild AD osteopetrosis form ≈5.5/100,000 in a Danish population survey (32/33 patients had the AD form) (PMID: 3829443). Incidence not separately quantified.
Inheritance: Autosomal dominant, heterozygous LRP5 gain of function (PMID: 12579474).
Penetrance: Incomplete — two obligate carriers were phenotypically unaffected (PMID: 3829443).
Expressivity: Highly variable, age-dependent (PMID: 3829443).
Anticipation / mosaicism / founder effects: Not established (non-repeat disorder). Certain alleles (e.g., A242T) recur across multiple families (found in 9 families), but true founder effects are unproven (PMID: 38909879).
Consanguinity / carrier frequency: Not relevant (dominant); "carrier" ≈ affected allele carrier.
Demographics: Reported across populations (notably Danish kindreds for ADO-I); no strong sex bias documented; age distribution skews toward detection in adolescence/adulthood.

10. Diagnostics

Imaging (primary): Skeletal radiographs and CT show generalized osteosclerosis maximal at the cranial vault with cortical thickening and reduced medullary cavity; DXA confirms markedly elevated BMD (no overlap with controls) (PMID: 3377922, PMID: 7605703). Distinguish from ADO-II's rugger-jersey/sandwich vertebrae and endobones (PMID: 10617161).
Laboratory: Low bone turnover — serum acid phosphatase normal/low in Type I (elevated in Type II); phosphate occasionally low (PMID: 3377922, PMID: 3829443). Serum SOST/DKK1/SFRP-4 are normal — not diagnostic biomarkers (PMID: 24927689).
Genetic testing: Targeted LRP5 single-gene sequencing (E1 domain) or sclerosing-bone-dysplasia gene panel; WES/WGS where the panel is negative. Radiologic-plus-genetic paradigm (PMID: 42096006). Karyotype/CMA/FISH/mtDNA/repeat testing: not applicable.
Differential diagnosis: ADO-II (CLCN7, fracture-prone, sandwich vertebrae); pycnodysostosis; sclerosteosis/van Buchem (SOST); Camurati-Engelmann (TGFB1); Worth endosteal hyperostosis (LRP5 spectrum overlap) (PMID: 18328982, PMID: 37659026).
Screening: Cascade genetic testing of first-degree relatives after an index diagnosis.

11. Outcome / Prognosis

Survival/mortality: Life expectancy is essentially normal; ADO-I is a "benign" osteopetrosis, in contrast to malignant infantile (recessive) osteopetrosis, though the "benign" label understates cranial risk (PMID: 38483591).
Morbidity/function: Driven by cranial-nerve compression (hearing loss, trigeminal neuralgia, visual loss), dental abscess, and rare marrow issues — "often underestimated and neglected" (PMID: 38593953). Fractures are NOT increased and bone is intrinsically strong (PMID: 12054167, PMID: 20503060).
Recovery: Surgical decompression of cranial-nerve compression can give durable relief (5-year sustained) (PMID: 41431003).
Prognostic factors: Location/severity of cranial hyperostosis and specific allele (magnitude/surface selectivity differ) (PMID: 42113468). No validated molecular prognostic biomarker.

12. Treatment

Pharmacotherapy: No curative or disease-modifying drug. Supportive vitamin D/calcium; complication management (PMID: 42096006). Anti-resorptives (bisphosphonates/denosumab) are not indicated — resorption is not the problem. (NCIT: vitamin D therapy, calcium supplement.)
HSCT: The treatment of choice for osteoclast-defect (recessive) osteopetroses, but mechanistically inapplicable to LRP5/osteoblast-driven ADO-I (PMID: 42096006). (NCIT: hematopoietic stem cell transplantation.)
Surgical/interventional: Decompressive surgery for cranial-nerve compression (e.g., staged posterior-fossa decompression + microvascular decompression for trigeminal neuralgia) — durable (PMID: 41431003); orthopedic surgery for the rare fracture is technically demanding in sclerotic bone. (NCIT: surgical procedure; microvascular decompression.)
Supportive/rehabilitative: Audiology, ophthalmology, dental care, pain management, multidisciplinary follow-up (PMID: 38593953).
Therapeutic significance (mirror image): ADO-I biology validated the anti-sclerostin (romosozumab) and anti-DKK1 anabolic osteoporosis strategy — blocking these inhibitors phenocopies the ADO-I gain of function and synergistically raises bone mass (PMID: 29875318, PMID: 17395698, PMID: 39447984).

13. Prevention

Primary prevention: Not possible (monogenic, germline). Genetic counseling is the mainstay — autosomal dominant, 50% transmission risk per child, with the caveat of incomplete penetrance and variable expressivity (PMID: 3829443).
Secondary prevention: Cascade testing and periodic surveillance (audiology, ophthalmology, neuro-imaging) to catch cranial-nerve compression early.
Tertiary prevention: Timely surgical decompression to prevent permanent neural deficit (PMID: 41431003).
Reproductive options: Preimplantation/prenatal genetic testing available where a familial variant is known. Immunization/public-health/environmental measures: not applicable.

14. Other Species / Natural Disease

Taxonomy/orthologs: LRP5 is conserved; mouse Lrp5 (NCBI Gene 16973; MGI:1278315) is the principal ortholog used to model the disease.
Natural disease: No well-characterized spontaneous ADO-I analog is documented in companion animals in the reviewed literature; the strongest cross-species evidence is engineered mouse models (below). Comparative biology: the Wnt/LRP5 bone-mass axis is evolutionarily conserved, and mouse HBM alleles faithfully reproduce the human direction of effect.
Zoonotic potential: Not applicable (non-infectious, genetic).

15. Model Organisms

Model	Type	Phenotype recapitulation	Reference
Human LRP5 G171V transgenic mouse	Transgenic (mammalian)	HBM, greater bone mass & biomechanical performance; +48% intrinsic modulus	PMID: 20503060
Lrp5 p.G171V & p.A214V knock-in mice	Knock-in	HBM; resistant to SOST/DKK1-induced osteopenia	PMID: 25808845
Lrp5 p.A214V knock-in	Knock-in	Increased bone mass & strength via enhanced Wnt; rescues OI model	PMID: 27297606
Lrp5 A241T transgenic (≈human A242T)	Transgenic	HBM phenotype reproduced; enhances implant osseointegration	PMID: 38909879, PMID: 41025443
Lrp5 knockout	Knockout (contrast)	LOW bone mass (opposite pole) — confirms directionality	PMID: 31437568
Combined G171V/A214V knock-in	Knock-in	No additive benefit; probes surface-selective mechanism	PMID: 42113468

Applications: Dissecting Wnt-inhibitor resistance, bone material properties, GxE (dietary calcium/vitamin D), and validating anti-SOST/anti-DKK1 anabolic strategies. Limitations: mouse models capture the HBM/strength phenotype well but do not fully model human skull-base cranial-nerve compression; the G171V membrane-localization paradox remains unresolved (PMID: 42113468). Resources: MGI (mouse Lrp5, MGI:1278315).

Mechanistic Model / Interpretation

ADO-I is best understood as a single-node dysregulation of the Wnt/LRP5 bone-mass rheostat. LRP5 integrates activating Wnt ligands against inhibitory SOST and DKK1 at its E1 β-propeller. In health, osteocyte-derived sclerostin tunes down osteoblast Wnt signaling to keep bone formation in check. ADO-I mutations physically remove the inhibitor "off-switch" from a single receptor surface, so the osteoblast receives an unopposed "build" signal for life. The result is more bone — and, because Wnt-built bone has superior intrinsic material properties, stronger bone. This is the mechanistic explanation for the single most distinctive clinical feature of the disease: it is the only osteopetrosis without excess fractures.

The same node explains the disease's paradoxes: - Osteoclasts are normal because the lesion is upstream in the osteoblast; osteoclast changes seen in vivo are secondary. - Skull-predominant morbidity follows because the skull is where excess formation causes the most mechanical mischief (foraminal narrowing), not because the skull is uniquely susceptible at the molecular level. - Bidirectionality of LRP5 (OPPG at the loss-of-function pole, HBM at the gain-of-function pole) makes ADO-I a natural human experiment that de-risked anti-sclerostin/anti-DKK1 drug development — patients constitutively embody the very pharmacology those drugs deliver.

Axis	ADO-I (gain of function)	ADO-II / CLCN7 (contrast)	LRP5-LOF / OPPG (opposite pole)
Defective cell	Osteoblast (Wnt signaling)	Osteoclast (acidification)	Osteoblast (Wnt signaling)
Bone mass	↑↑ (age-progressive)	↑↑	↓↓
Fracture risk	Not increased	Increased (78%)	Increased
Skull vault	Marked thickening	Variable	Low mass
HSCT	Not applicable	Not curative in AD form	Not applicable

Evidence Base

PMID	Contribution	Supports
12054167	Maps ADO-I to 11q12-13; defines cranial-vault phenotype & no-fracture rule	F001, F003
12579474	Six novel N-terminal LRP5 HBM mutations	F001, F008
20855225	Reclassification of ADO-I as HBM disease	F001
18521528	HBM-LRP5 resists DKK1/sclerostin (in vitro)	F002
25808845	In vivo proof of inhibitor resistance in knock-ins	F002, F006
16251418	T253I osteoclasts intrinsically normal	F002
24927689	Circulating SOST/DKK1/SFRP4 normal	F002, F009
21944579	E1 propeller = inhibitor docking; mutations cluster there	F008
3377922	Original two-type classification; cortical thickening	F004, F009
7605703	DXA: +51% axial BMD, age-progressive	F004
3829443	Prevalence 5.5/100k, incomplete penetrance, 39% asymptomatic	F005
20503060	G171V transgenic: +48% modulus, superior strength	F006
27297606	A214V knock-in improves strength; rescues OI	F006, F010
10617161	ADO-II fracture-prone contrast (78%)	F003
37659026	LRP5-HBM spectrum phenotype frequencies	F003, F007
41431003	Trigeminal neuralgia; durable surgical decompression	F007, F010
38593953	Underrecognized adult osteopetrosis complications	F007
42096006	Diagnostic/therapy paradigm; HSCT scope	F009, F010
29875318	Anti-SOST + anti-DKK1 synergy (mirror image)	F010
42113468	Allele-specific magnitude/surface effects; G171V paradox	F006, mechanism

Supporting/context papers: 17395698, 39447984, 40940800, 40255261, 38909879, 41025443, 38477773, 31437568, 18328982, 38483591.

Limitations and Knowledge Gaps

Nosological overlap. ADO-I, LRP5-HBM, and Worth-type endosteal hyperostosis form a continuum; some cited frequencies (e.g., facial changes 61%, torus palatinus 41%) derive from the broader spectrum rather than genetically confirmed ADO-I alone (PMID: 37659026).
Epidemiology is dated and geographically narrow. The 5.5/100,000 prevalence and penetrance estimates rest chiefly on one Danish survey (PMID: 3829443); modern multi-ethnic, genotype-confirmed prevalence and sex-ratio data are lacking.
Genotype–phenotype correlation is incomplete. Alleles differ in magnitude and skeletal-surface selectivity, but predictors of who develops cranial-nerve compression are unknown (PMID: 42113468).
Mechanistic loose end. The G171V receptor causes HBM despite poor plasma-membrane localization — its mechanism "remains elusive" (PMID: 42113468).
No disease-specific therapy or trials. Management is generic/supportive; no ADO-I-targeted pharmacology (e.g., a rational Wnt-dampening approach) has been tested.
Biomarkers absent. Circulating Wnt inhibitors are not diagnostic or prognostic (PMID: 24927689); no molecular marker predicts cranial complications.

Proposed Follow-up Experiments / Actions

Genotype-stratified natural-history registry. Prospectively enroll genetically confirmed ADO-I patients to quantify per-allele penetrance, age-of-onset distributions, sex ratio, and the incidence/timing of cranial-nerve compression.
Predictive imaging biomarkers. Correlate quantitative skull-base CT foraminal metrics with cranial-nerve outcomes to build a risk-stratification tool that triggers earlier prophylactic decompression.
Resolve the G171V paradox. Use surface-biotinylation, live-cell receptor trafficking, and structural studies to determine how a poorly membrane-localized receptor drives HBM (PMID: 42113468).
Rational therapeutic test in models. Since ADO-I is Wnt-over-signaling, test whether pharmacologic Wnt-inhibitor delivery (recombinant sclerostin/DKK1 agonism or LRP5-E1-targeting antibodies) can selectively dampen skull hyperostosis in A241T/A214V mice without inducing systemic osteopenia.
Auditory/ophthalmologic surveillance protocol. Formalize and validate a multidisciplinary screening schedule to catch reversible cranial-nerve deficits early (PMID: 38593953).
Comparative-genetics screen. Search veterinary/OMIA resources and companion-animal cohorts for naturally occurring LRP5-HBM analogs to broaden the comparative model base.
MONDO/ontology curation. Formalize the ADO-I MONDO entry and precise HP/UBERON/CL annotations (E1-domain gain of function; cranial-nerve compression; osteoblast-driven cortical osteosclerosis) for knowledge-base integration.

Report compiled from a five-iteration autonomous investigation: 10 confirmed findings, 44 papers reviewed. Evidence source types span human clinical (family/cohort/case studies), model organism (knock-in/transgenic/knockout mice), in vitro (receptor-binding assays), and computational (in silico variant analysis, structural biology).

Artifacts

Term Validation

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

Outcome	Count
Terms checked	24
Resolved	21
Unresolved (possible confabulation)	0
Obsolete	0
Unverifiable	3
Terms whose name was checked	6
Terms named correctly	4
Terms named as a different term	1
Terms whose name is worth a second look	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:

HP:0011001 (2 mentions) - the report calls it "Universal (no overlap with controls)"; HP calls it Increased bone mineral density

Terms whose name is worth a second look

The report's name for these is recognisably related to the term's own name without being one of them. A loose paraphrase reads the same way as a citation of the wrong sibling term - and so does a related synonym, which the ontology records precisely because it names something adjacent rather than the same thing - so these are listed rather than judged:

GO:0005886 (2 mentions) - the report calls it "Subcellular: LRP5 at the plasma membrane"; GO calls it plasma membrane**, and lists "cellular membrane" among its other names

Prefixes with no resolver

Terms carrying these prefixes were not checked either way, because no configured ontology covers them. An unrecognised prefix may name an ontology this run could not reach as easily as one that does not exist, so nothing here is evidence of fabrication: ORPHA, MGI.

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome	Count
References checked	30
Resolved	30
Unresolved (possible confabulation)	0
Unverifiable	0
Quoted claims checked	13
Quoted claims found in source	13
Quoted claims not found in source	0
References weighed for topical relevance	30
On topic	21
Off topic	0

All extracted references resolved successfully.

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Discussions and Knowledge Gaps

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Diagnosis

Progression

Prevalence

Differential Diagnoses

Animal Models

Source YAML

References & Deep Research

References

Deep Research

Key Findings

Finding 1 — ADO-I is an LRP5 gain-of-function high-bone-mass disorder (11q13) [human clinical]

Finding 2 — Mechanism: mutant LRP5 resists sclerostin/DKK1, causing constitutive Wnt/β-catenin signaling [in vitro + mouse]

Finding 3 — Clinical phenotype: generalized osteosclerosis maximal at the cranial vault, often asymptomatic, uniquely NOT fracture-prone [human clinical]

Finding 4 — Markedly increased, age-progressive, cortical-predominant BMD; skull-vault thickening is the defining radiographic feature [human clinical]

Finding 5 — Epidemiology & inheritance: AD, incompletely penetrant, variably expressed; prevalence ≈5.5/100,000 [human clinical]

Finding 6 — Mouse models: HBM knock-ins reproduce strong bone; Lrp5-knockout does the opposite [mouse]

Finding 7 — Principal morbidity is cranial-nerve compression from skull-base hyperostosis, not fracture [human clinical]

Finding 8 — Structural basis: mutations map to the E1 β-propeller, the sclerostin/DKK1 docking module [structural/computational]

Finding 9 — Diagnosis is radiologic + LRP5 sequencing, with low/normal bone-turnover chemistry [human clinical]

Finding 10 — Management is supportive/surgical; the mechanism validates anti-sclerostin/anti-DKK1 osteoporosis drugs [human clinical + mouse]

Full Section-by-Section Report

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

Mechanistic Model / Interpretation

Evidence Base

Limitations and Knowledge Gaps

Proposed Follow-up Experiments / Actions

Artifacts

Term Validation

Terms the report names something else

Terms whose name is worth a second look

Prefixes with no resolver

Reference Validation