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Classifications

Lysosomal Storage

ICIMD (Inherited Metabolic Disorders)

ISDS Skeletal Nosology

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Mappings

MONDO

MONDO:0011758 Hurler syndrome

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Inheritance

1

Autosomal recessive inheritance HP:0000007

Hurler syndrome is the severe autosomal recessive form of mucopolysaccharidosis type I caused by biallelic pathogenic variants in IDUA.

Autosomal recessive inheritance

Show evidence (1 reference)

PMID:32780955 SUPPORT Human Clinical

"Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder, caused by deficiency of α-L-iduronidase, and consequent accumulation of dermatan and heparan sulfates."

This directly supports autosomal recessive inheritance for severe MPS I, the Hurler phenotype.

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Mechanistic Hypotheses

1

Canonical IDUA Deficiency / Glycosaminoglycan Lysosomal Storage Model

canonical_idua_deficiency_gag_lysosomal_storage_model CANONICAL

Evidence balance 3 support

Mucopolysaccharidosis type I — Hurler syndrome (severe), Hurler-Scheie (intermediate), and Scheie (attenuated) — is an autosomal recessive lysosomal storage disorder caused by loss-of-function variants in IDUA encoding α-L-iduronidase. Loss of α-L-iduronidase activity prevents lysosomal degradation of heparan sulfate and dermatan sulfate, producing pathological GAG accumulation in lysosomes of multiple cell types. Substrate storage drives progressive coarsening, dysostosis multiplex, hepatosplenomegaly, cardiac valvular and myocardial disease, corneal clouding, recurrent airway obstruction, and (in severe Hurler) progressive neurodevelopmental regression. Hematopoietic stem cell transplantation (the standard of care for severe Hurler before age 2), enzyme replacement therapy (laronidase), and emerging gene therapy approaches corroborate the IDUA-deficiency / GAG-accumulation axis as the canonical pathogenic mechanism.

Retained as CANONICAL with an expansion to include secondary cascades. The 2026 openscientist hypothesis-search report (kb/hypotheses/Hurler_syndrome/canonical_idua_deficiency_gag_lysosomal_storage_model) finds the model strongly supported; see the assessment sidecar assessments/openscientist-assessment-by-claude-opus-5.yaml for the claim-by-claim disposition. IDUA deficiency is the necessary upstream cause: residual enzyme activity maps quantitatively to clinical severity (Hurler 0.18%, Hurler-Scheie 0.27%, Scheie 0.79% of normal in patient fibroblasts); laronidase reduces urinary GAGs by about 65% over 26 weeks; normal post-HCT enzyme levels predict superior long-term outcomes across organ systems (n=217 multicenter); and homozygous IDUA pseudodeficiency alleles produce no clinically relevant excess of MPS I features in 1,803 adults. Critical refinement: GAG accumulation alone is necessary but NOT sufficient for the full clinical phenotype. Secondary cascades appear integral to pathogenesis: (1) an immune contribution to cardiovascular disease, shown in mice as inflammasome upregulation with medial macrophage and adventitial T-cell infiltration of the ascending aorta in immunocompetent but not immunodeficient MPS I animals, with the human counterpart untested (see the HUMAN_MODEL_MISMATCH discussion); (2) neuroinflammation with microglial activation and cytokine release; (3) cathepsin B leakage from destabilized lysosomes; (4) secondary ganglioside accumulation; (5) oxidative stress and mitochondrial dysfunction; and (6) disrupted signaling by extracellular glycosaminoglycan (FGF and Wnt pathway interactions). Residual disease burden persists after successful enzyme correction, but whether that reflects self-sustaining secondary cascades or irreversible pre-treatment damage plus poor enzyme delivery to avascular tissue is unresolved (see the KNOWLEDGE_GAP discussion). HCT (severe Hurler), ERT (laronidase, all subtypes), and investigational AAV-IDUA gene therapy validate the canonical upstream axis. Three numbers or attributions that appeared in an earlier version of this note were provider inference rather than source content and have been removed: a ">1.8% residual activity" pseudodeficiency cut-off, mast-cell activation as the immune mechanism in valves and myocardium, and IGF and BMP as the disrupted growth-factor pathways.

Deep research

OpenScientist citations 49 citations 2026-05-24T16:42:20.660916

Show evidence (3 references)

PMID:32780955 SUPPORT Other

"Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder, caused by deficiency of α-L-iduronidase, and consequent accumulation of dermatan and heparan sulfates."

Existing canonical mechanism citation in the dismech knowledge base, used as the seed for the hypothesis-search deep-research run.

PMID:23786846 SUPPORT In Vitro

"Mean residual IDUA activity was 0.18% (range 0-0.6) of the control value in MPS IH fibroblasts (n=5); against 0.27% (range 0.2-0.3) in MPS IH/S cells (n=3); and 0.79% (range 0.3-1.8) in MPS IS fibroblasts (n=5)."

Residual alpha-L-iduronidase activity measured in patient fibroblasts tracks MPS I subtype severity, with Hurler at the lowest end of the gradient. This is the quantitative support for the enzyme-deficiency axis of the hypothesis. The series is small (13 cell lines in total) and its authors present it as a phenotype-prediction aid rather than as a threshold.

PMID:39559959 SUPPORT Human Clinical

"We found no clinically relevant significant differences between cases and controls nor genotype-phenotype associations across four alleles."

Adults homozygous for IDUA pseudodeficiency alleles, which lower in vitro enzyme activity without abolishing it, show no excess of MPS I features against matched controls. This supports severe loss of alpha-L-iduronidase activity, rather than any reduction, as the requirement for disease. Ascertainment is by electronic medical record within a hospital biorepository, and the study reports no enzyme activity values.

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Discussions and Knowledge Gaps

2

Does the immune activation that is required for aortic dilation in immunocompetent MPS I mice also mediate aortic and valvular disease in human Hurler syndrome?

HUMAN MODEL MISMATCH OPEN mismatch_hurler_immune_requirement_for_aortic_disease

Attached to

pathophysiology#Progressive skeletal and multisystem organ injury phenotypes#Abnormal heart valve morphology

Immunocompetent C57BL/6 MPS I mice develop ascending aortic dilation, aortic insufficiency and reduced left ventricular function, while immunodeficient NSG MPS I mice with the same degree of urinary glycosaminoglycan elevation do not. The immunocompetent aortas upregulated all eleven components of the inflammasome pathway and carried medial macrophage and adventitial T-cell infiltrates that the immunodeficient aortas lacked. If that dependency holds in people, glycosaminoglycan storage is not by itself sufficient for the cardiac phenotype, and anti-inflammatory adjunctive therapy becomes a plausible addition to enzyme restoration. Three things keep this out of the causal graph. The study is small, with 12 immunocompetent and 8 immunodeficient mutant male mice, and its authors describe it as a preliminary study. Tissue glycosaminoglycan was never quantified, only urinary excretion, so equivalent storage in the aortic wall is assumed rather than shown. The two strains differ in genetic background as well as in immune competence. No human study has tested immune suppression or inflammasome blockade for MPS I cardiovascular disease.

Proposed experiments

Immune profiling of explanted MPS I cardiac valve and aortic tissue

mps1_valve_inflammasome_immunoprofiling

Immunohistochemical and transcriptional profiling of valve and aortic tissue removed at surgery from MPS I patients against age-matched non-MPS surgical controls, scoring macrophage and T-cell infiltration and inflammasome component expression alongside a quantitative measure of tissue glycosaminoglycan storage rather than staining intensity alone.

Would support

pathophysiology#Progressive skeletal and multisystem organ injury phenotypes#Abnormal heart valve morphology

Supporting outcome

Macrophage and T-cell infiltration with inflammasome component upregulation in MPS I valve and aortic tissue, scaling with lesion severity rather than with storage burden alone.

Refuting outcome

Storage-laden MPS I valve tissue showing no more immune infiltration or inflammasome expression than controls, which would confine the mouse finding to the model.

Show evidence (2 references)

PMID:35165009 SUPPORT Model Organism

"Ascending aortic diameters were significantly greater, left ventricular function significantly decreased, and AI significantly more frequent in B6 MPSI mice compared to NSG MPSI mice (p < 0.0001, p = 0.008 and p = 0.02, respectively); NSG and B6 WT mice showed no changes."

The cardiac phenotype separates immunocompetent from immunodeficient MPS I mice, which is the observation that makes translation to human disease the open question recorded here.

PMID:35165009 SUPPORT Model Organism

"These results suggest that the innate and adaptive immune systems play a role in these cardiac findings which may be relevant to human MPSI."

The authors state human relevance as a suggestion rather than a demonstrated result, which is precisely the mismatch this discussion records.

Why does considerable residual disease burden persist in every successfully transplanted Hurler patient, and does it reflect secondary cascades that have become independent of ongoing glycosaminoglycan storage?

KNOWLEDGE GAP OPEN gap_hurler_residual_disease_after_enzyme_restoration

Attached to

treatments#Hematopoietic stem cell transplantation pathophysiology#Dermatan sulfate and heparan sulfate accumulation

Transplantation restores donor-derived alpha-L-iduronidase, and a normal post-transplant enzyme level predicts superior long-term outcomes across organ systems. Yet residual burden requiring corrective surgery is observed in all patients at every decade of follow-up, and restrictive lung disease is present in every treated patient able to complete testing. Two explanations fit these data and have not been separated. Damage may accrue irreversibly before transplantation, which is typically performed near two years of age, and circulating enzyme may reach avascular cartilage, bone, heart valve and cornea poorly, which is what the enzyme replacement literature already reports. Alternatively, secondary cascades downstream of storage may become self-sustaining and stop responding to substrate clearance. Which is right determines whether the remedy is earlier or better enzyme delivery, or a second agent aimed at a downstream cascade. Serial multi-omic sampling from before transplantation through several years afterwards, and conditional restoration of Idua at different disease stages in animals, would separate them.

Show evidence (1 reference)

PMID:33517895 SUPPORT Human Clinical

"Despite HSCT, considerable residual disease burden and ensuing corrective surgical interventions were observed in all, and at every decade of follow-up post HSCT."

Three decades of follow-up in 25 successfully transplanted Hurler patients establish the observation this gap is about: enzyme restoration that is sufficient to change the natural history does not stop somatic disease accruing.

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Pathophysiology

4

IDUA enzyme deficiency

Hurler syndrome results from severe alpha-L-iduronidase deficiency caused by biallelic loss of IDUA function.

IDUA hgnc:5391 ⚠ ABNORMAL

IDUA hgnc:5391

glycosaminoglycan catabolic process GO:0006027 ↓ DECREASED

alpha-L-iduronidase activity GO:0003940 ↓ DECREASED

Downstream

Dermatan sulfate and heparan sulfate accumulation Loss of alpha-L-iduronidase blocks lysosomal clearance of dermatan sulfate and heparan sulfate

Alpha-L-iduronidase activity Severe IDUA loss is directly reflected by deficient alpha-L-iduronidase enzyme activity.

Show evidence (1 reference)

PMID:32780955 SUPPORT Human Clinical

"Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder, caused by deficiency of α-L-iduronidase, and consequent accumulation of dermatan and heparan sulfates."

This directly states the core alpha-L-iduronidase enzyme deficiency in Hurler syndrome.

Dermatan sulfate and heparan sulfate accumulation

Loss of IDUA blocks lysosomal degradation of dermatan sulfate and heparan sulfate, causing progressive glycosaminoglycan storage in cells and connective tissues.

lysosome GO:0005764

Downstream

Progressive skeletal and multisystem organ injury Glycosaminoglycan storage drives progressive skeletal, visceral, cardiac, and CNS injury

CNS glycosaminoglycan storage injury Heparan-sulfate-containing storage disease contributes to severe CNS involvement in Hurler syndrome.

Dermatan sulfate Dermatan sulfate accumulation is one of the core stored substrates in MPS I.

Heparan sulfate Heparan sulfate accumulation is one of the core stored substrates in MPS I.

Urinary glycosaminoglycans Cellular glycosaminoglycan storage is reflected by abnormal urinary GAG excretion.

Show evidence (2 references)

PMID:32780955 SUPPORT Human Clinical

"Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder, caused by deficiency of α-L-iduronidase, and consequent accumulation of dermatan and heparan sulfates."

This directly supports dermatan sulfate and heparan sulfate accumulation as the immediate biochemical consequence of IDUA deficiency.

PMID:28595941 SUPPORT Human Clinical

"MPS I with either severe or attenuated form has limited activity of the enzyme α-L-iduronidase (IDUA) that breaks down DS and HS. These GAGs remain stored in cells causing progressive damage of various tissues including bone and, in severe cases, brain."

This supports persistent DS and HS storage as the central substrate accumulation mechanism in severe MPS I.

CNS glycosaminoglycan storage injury

In severe MPS I, glycosaminoglycan storage extends to the brain and drives the Hurler neurologic branch, including early developmental delay and enlarged head circumference.

lysosome GO:0005764

Downstream

Global developmental delay Severe CNS storage involvement contributes to early developmental delay.

Macrocephaly Severe early Hurler involvement includes enlarged head circumference.

Show evidence (1 reference)

PMID:28595941 SUPPORT Human Clinical

"These GAGs remain stored in cells causing progressive damage of various tissues including bone and, in severe cases, brain."

This directly supports brain involvement from glycosaminoglycan storage in severe MPS I.

Progressive skeletal and multisystem organ injury

Glycosaminoglycan storage in connective tissues drives progressive dysostosis multiplex, kyphosis, joint restriction, organomegaly, ocular disease, and cardiac involvement beginning in infancy. In severe Hurler syndrome, clinical signs emerge within the first months of life and the disease progresses rapidly.

chondrocyte CL:0000138

Downstream

Dysostosis multiplex Skeletal glycosaminoglycan storage manifests as dysostosis multiplex in severe MPS I.

Coarse facial features Multisystem storage disease includes progressive coarse facial morphology.

Corneal opacity Ocular storage involvement manifests clinically as corneal clouding.

Hearing impairment Otolaryngologic involvement in Hurler syndrome includes hearing loss.

Hepatosplenomegaly Visceral storage involvement causes liver and spleen enlargement.

Global developmental delay Severe CNS involvement in Hurler syndrome contributes to early developmental delay.

Joint stiffness Connective-tissue storage manifests as early joint restriction and stiffness.

Abnormal heart valve morphology Cardiac storage involvement includes thickening of the heart valves.

Growth delay Severe somatic storage disease includes impaired growth.

Kyphosis Skeletal storage disease includes early kyphosis.

Umbilical hernia Connective-tissue and abdominal-wall involvement includes umbilical hernia.

Inguinal hernia Connective-tissue and abdominal-wall involvement includes inguinal hernia.

Recurrent otitis media Early otolaryngologic involvement includes otitis media.

Recurrent respiratory infections Early upper-airway and respiratory involvement includes frequent respiratory infections.

Obstructive Sleep Apnea / Upper Airway Obstruction Multisystem respiratory involvement in MPS I includes upper-airway obstruction and obstructive sleep apnea.

Show evidence (2 references)

PMID:32780955 SUPPORT Human Clinical

"A prominent clinical manifestation of MPS-IH is dysostosis multiplex, a constellation of skeletal abnormalities."

This supports severe skeletal tissue involvement as a central downstream consequence of Hurler pathophysiology.

PMID:28193245 SUPPORT Human Clinical

"Nearly all patients (98%) showed signs of disease during the first 6 months of life."

This infant cohort directly supports the rapid early multisystem progression characteristic of Hurler syndrome.

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Pathograph

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

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Phenotypes

16

Cardiovascular 2

Hepatosplenomegaly HP:0001433

Show evidence (1 reference)

PMID:28595941 SUPPORT Human Clinical

"Typical manifestations include coarse face, corneal clouding, developmental delay, mental retardation, growth retardation, contractures of the joints, kyphoscoliosis, dysostosis multiplex, hearing loss, thickening of the heart valves, hepatosplenomegaly, and umbilical and inguinal hernias."

This directly lists hepatosplenomegaly among typical severe MPS I manifestations.

Abnormal heart valve morphology HP:0001654

Show evidence (1 reference)

PMID:28595941 SUPPORT Human Clinical

"Typical manifestations include coarse face, corneal clouding, developmental delay, mental retardation, growth retardation, contractures of the joints, kyphoscoliosis, dysostosis multiplex, hearing loss, thickening of the heart valves, hepatosplenomegaly, and umbilical and inguinal hernias."

This specifically identifies heart-valve thickening among the typical manifestations of severe MPS I.

Digestive 2

Umbilical hernia HP:0001537

Show evidence (1 reference)

PMID:28595941 SUPPORT Human Clinical

"Typical manifestations include coarse face, corneal clouding, developmental delay, mental retardation, growth retardation, contractures of the joints, kyphoscoliosis, dysostosis multiplex, hearing loss, thickening of the heart valves, hepatosplenomegaly, and umbilical and inguinal hernias."

The review directly lists umbilical hernia among typical severe MPS I manifestations.

Inguinal hernia HP:0000023

Show evidence (1 reference)

PMID:28595941 SUPPORT Human Clinical

"Typical manifestations include coarse face, corneal clouding, developmental delay, mental retardation, growth retardation, contractures of the joints, kyphoscoliosis, dysostosis multiplex, hearing loss, thickening of the heart valves, hepatosplenomegaly, and umbilical and inguinal hernias."

The review directly lists inguinal hernia among typical severe MPS I manifestations.

Ear 2

Hearing impairment HP:0000365

Show evidence (1 reference)

PMID:28193245 SUPPORT Human Clinical

"Common early disease manifestations included failed newborn hearing screen, respiratory symptoms, difficulty latching, and otitis media."

Failed newborn hearing screening is partial but clinically meaningful support for early hearing impairment in Hurler syndrome.

Recurrent otitis media HP:0000403

Show evidence (1 reference)

PMID:28193245 SUPPORT Human Clinical

"Common early disease manifestations included failed newborn hearing screen, respiratory symptoms, difficulty latching, and otitis media."

This directly identifies otitis media among common early manifestations; PARTIAL because the snippet documents otitis media without explicitly establishing the recurrence captured by HP:0000403.

Eye 1

Corneal opacity HP:0007957

Show evidence (2 references)

PMID:28193245 SUPPORT Human Clinical

"Other symptoms such as kyphosis, corneal clouding, cardiac disease, joint restrictions, and enlarged head circumference typically appeared slightly later (median age, 8-10 months)."

The infant natural-history cohort directly documents corneal clouding as an early Hurler manifestation.

PMID:8907377 SUPPORT Model Organism

"The corneal clouding was the result of storage in stromal keratocytes rather than corneal edema from endothelial dysfunction."

Morphologic study of MPS I cat, MPS VI cat, and MPS VII dog corneas locates the lesion in stromal keratocytes. MPS I endothelium carried abundant lysosomal inclusions yet still maintained corneal dehydration normally, so the clouding is a stromal storage lesion rather than endothelial decompensation. This grounds the cellular substrate of the phenotype; it is animal morphology and does not by itself speak to the human frequency or course.

Head and Neck 2

Coarse facial features VERY_FREQUENT HP:0000280

Show evidence (2 references)

PMID:28595941 SUPPORT Human Clinical

"Typical manifestations include coarse face, corneal clouding, developmental delay, mental retardation, growth retardation, contractures of the joints, kyphoscoliosis, dysostosis multiplex, hearing loss, thickening of the heart valves, hepatosplenomegaly, and umbilical and inguinal hernias."

This review explicitly lists coarse facial appearance among the typical manifestations of severe MPS I.

ORPHA:93473 SUPPORT Other

"HP:0000280 | Coarse facial features | Very frequent (99-80%)"

Orphanet records coarse facial features as very frequent in Hurler syndrome, supporting the VERY_FREQUENT frequency band.

Macrocephaly HP:0000256

Show evidence (1 reference)

PMID:28193245 SUPPORT Human Clinical

"Other symptoms such as kyphosis, corneal clouding, cardiac disease, joint restrictions, and enlarged head circumference typically appeared slightly later (median age, 8-10 months)."

Enlarged head circumference is direct support for macrocephaly.

Immune 1

Recurrent respiratory infections HP:0002205

Show evidence (1 reference)

PMID:20301341 SUPPORT Human Clinical

"Typical early manifestations are nonspecific (e.g., umbilical or inguinal hernia, frequent upper respiratory tract infections before age 1 year)."

This GeneReviews summary directly supports recurrent respiratory infections as an early severe MPS I feature.

Musculoskeletal 3

Dysostosis multiplex HP:0000943

Show evidence (1 reference)

PMID:32780955 SUPPORT Human Clinical

"A prominent clinical manifestation of MPS-IH is dysostosis multiplex, a constellation of skeletal abnormalities."

This directly identifies dysostosis multiplex as a prominent Hurler phenotype.

Joint stiffness HP:0001387

Show evidence (1 reference)

PMID:28193245 SUPPORT Human Clinical

"Other symptoms such as kyphosis, corneal clouding, cardiac disease, joint restrictions, and enlarged head circumference typically appeared slightly later (median age, 8-10 months)."

The abstract reports joint restrictions rather than the exact ontology wording, so this is partial support for the closely related phenotype of joint stiffness.

Kyphosis HP:0002808

Show evidence (1 reference)

PMID:28595941 SUPPORT Human Clinical

"Patients with Hurler syndrome develop initial symptoms like hernias, hepatomegaly, kyphosis and developmental delay within a year and die within a decade if untreated"

This directly identifies kyphosis as an early Hurler manifestation.

Nervous System 2

Obstructive Sleep Apnea / Upper Airway Obstruction HP:0002870

Show evidence (1 reference)

PMID:20301341 SUPPORT Other

"tonsillectomy and adenoidectomy for eustachian tube dysfunction and/or upper airway obstruction; ventilating tubes; hearing aids as needed; CPAP for sleep apnea"

GeneReviews documents CPAP for sleep apnea (alongside tonsillectomy/ adenoidectomy for upper-airway obstruction) in MPS I, directly naming the obstructive sleep apnea phenotype.

Global developmental delay HP:0001263

Show evidence (1 reference)

PMID:28595941 SUPPORT Human Clinical

"Patients with Hurler syndrome develop initial symptoms like hernias, hepatomegaly, kyphosis and developmental delay within a year and die within a decade if untreated"

This directly documents developmental delay as an early severe Hurler manifestation.

Growth 1

Growth delay HP:0001510

Show evidence (1 reference)

PMID:28595941 SUPPORT Human Clinical

"Typical manifestations include coarse face, corneal clouding, developmental delay, mental retardation, growth retardation, contractures of the joints, kyphoscoliosis, dysostosis multiplex, hearing loss, thickening of the heart valves, hepatosplenomegaly, and umbilical and inguinal hernias."

This directly supports growth retardation as a characteristic Hurler phenotype.

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Genetic Associations

1

IDUA (Loss-of-function)

Gene: IDUA hgnc:5391

Show evidence (3 references)

PMID:32780955 SUPPORT Human Clinical

"Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder, caused by deficiency of α-L-iduronidase, and consequent accumulation of dermatan and heparan sulfates."

This establishes alpha-L-iduronidase deficiency, i.e. loss of IDUA function, as the primary genetic cause of Hurler syndrome.

PMID:28595941 SUPPORT Human Clinical

"The two most common IDUA mutations are p.W402X and p.Q70X."

This supports noting p.W402X and p.Q70X as common IDUA alleles in MPS I.

PMID:31194252 SUPPORT Human Clinical

"About 67.6% of severe patients had genotypes where both variants identified are predicted to severely disrupt protein/gene function and 96.1% of attenuated patients had at least one missense or intronic variant."

In 538 registry patients with both IDUA alleles identified, the severe (Hurler) end of the spectrum is dominated by genotypes in which neither allele can produce functional enzyme, while attenuated disease almost always retains a missense or intronic allele. This is the genotype-level support for biallelic severe loss of function as the basis of Hurler syndrome specifically.

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Medical Actions

3

AAV-IDUA gene therapy (investigational)

Action: gene therapy Ontology label: Gene Therapy NCIT:C15238

Platform: Gene therapy

AAV-mediated IDUA gene therapy is in clinical development for severe MPS I. A first-in-human intracisternal AAV9-IDUA case reported durable neurodevelopmental benefit with >5-year follow-up. Multiple additional gene therapy strategies (intracerebroventricular AAV9, ex vivo lentiviral CD34+ HSC IDUA gene transfer) are in trials.

Mechanism Target:

RESTORES IDUA enzyme deficiency — AAV-delivered IDUA cDNA expressed in CNS or hematopoietic-progeny cells restores α-L-iduronidase activity and supports cross-correction of neighboring cells through mannose-6-phosphate receptor uptake.

Show evidence (1 reference)

PMID:41966056 SUPPORT Human Clinical

"Neurocognitive testing demonstrates ongoing acquisition of developmental abilities, with cognitive, speech, and motor age equivalents measuring one to two standard deviations below the normative mean. His neurodevelopment is significantly above the natural history of untransplanted Hurler..."

This is the single reported patient behind the first-in-human intracisternal AAV9-IDUA claim in the description. It is an open-label, uncontrolled, single-patient experience in which the child also continued weekly intravenous enzyme infusions throughout, so it supports therapeutic potential for the CNS branch rather than establishing that gene transfer corrects CNS disease.

Hematopoietic stem cell transplantation

Action: hematopoietic stem cell transplantation Ontology label: Hematopoietic Cell Transplantation NCIT:C15431

Platform: Cell therapy

Early hematopoietic stem cell transplantation is the standard disease-modifying therapy for severe Hurler syndrome and offers the best chance to preserve neurocognitive function. It is disease-modifying rather than curative: long-term follow-up of successfully transplanted patients documents considerable residual disease burden with corrective surgical interventions at every decade, and restrictive lung disease in every treated MPS I patient able to complete pulmonary function testing.

Mechanism Target:

RESTORES IDUA enzyme deficiency — Donor-derived hematopoiesis can restore alpha-L-iduronidase enzyme levels; normal post-HCT enzyme levels predict better long-term organ outcomes.

Show evidence (1 reference)

PMID:25624320 SUPPORT Human Clinical

"A normal α-l-iduronidase enzyme level obtained post-HCT was another highly significant predictor for superior long-term outcome in most organ systems."

This supports restored enzyme level as the proximal disease-modifying mechanism of HCT in Hurler syndrome.

Show evidence (3 references)

PMID:30442189 SUPPORT Human Clinical

"For severe MPS I patients (Hurler), early haematopoietic stem cell transplantation is the gold standard"

This directly names early HSCT as the gold-standard treatment for severe Hurler syndrome.

PMID:25624320 SUPPORT Human Clinical

"Preservation of cognitive function at HCT and a younger age at transplantation were major predictors for superior cognitive development posttransplant."

This large multicenter follow-up study supports early transplantation to preserve neurodevelopmental outcome.

PMID:32713717 SUPPORT Human Clinical

"All patients had restrictive lung disease. Cobb angle and male sex were significantly associated with more severe outcomes in the HSCT cohort, with 49% having severe to very severe disease."

Restrictive lung disease was present in every treated MPS I patient able to perform testing, and was severe or very severe in about half of the transplanted cohort. This supports the description's statement that transplantation modifies rather than eliminates the somatic disease.

Enzyme replacement therapy

Action: enzyme replacement therapy Ontology label: Protein Replacement Therapy NCIT:C16221

Intravenous laronidase improves somatic storage manifestations in Hurler syndrome but does not adequately treat central nervous system disease.

Mechanism Target:

INHIBITS Dermatan sulfate and heparan sulfate accumulation — Enzyme replacement reduces systemic glycosaminoglycan storage biomarkers and liver/spleen volume, while having limited penetration into cartilage, bone, eyes, and the CNS.

Show evidence (2 references)

PMID:30442189 SUPPORT Human Clinical

"While ERT is effective in reducing urinary glycosaminoglycans (GAGs) and liver and spleen volume, cartilaginous organs such as the trachea and bronchi, bones and eyes are poorly impacted by ERT probably due to limited penetration in the specific tissue."

Reduced urinary GAGs support inhibition of the glycosaminoglycan storage branch, with tissue-penetration limits noted by the review.

PMID:41163043 SUPPORT Human Clinical

"Laronidase consistently reduced uGAGs levels from baseline to week 26, with a percentage change of -64.61%"

A phase IV trial quantifies the size of the substrate-storage reduction achieved by laronidase, giving the INHIBITS link a magnitude rather than a direction alone. The trial is single-arm and open-label in 12 patients, and urinary GAG is a systemic surrogate that does not report cartilage, bone, eye, or CNS storage.

Show evidence (2 references)

PMID:30442189 SUPPORT Human Clinical

"Enzyme replacement therapy (ERT) is available for mucopolysaccharidosis (MPS) I, MPS II, MPS VI, and MPS IVA."

This directly confirms availability of enzyme replacement therapy for MPS I, including Hurler syndrome.

PMID:30442189 SUPPORT Human Clinical

"ERT in the present formulations also does not cross the blood-brain barrier, with the consequence that the central nervous system is not cured by ERT."

This explains the key limitation of ERT in severe Hurler syndrome, where CNS disease is clinically important.

🔬

Biochemical Markers

4

Alpha-L-iduronidase activity (DECREASED)

Context: Deficient alpha-L-iduronidase activity is the proximal biochemical defect in MPS I-Hurler.

Pathograph Readouts

Readout Of IDUA enzyme deficiency Negative Diagnostic

Low alpha-L-iduronidase enzyme activity directly reports the IDUA loss-of-function mechanism.

Show evidence (1 reference)

PMID:32780955 SUPPORT Human Clinical

"Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder, caused by deficiency of α-L-iduronidase, and consequent accumulation of dermatan and heparan sulfates."

This directly supports deficient alpha-L-iduronidase as the core biochemical abnormality.

Dermatan sulfate (INCREASED)

Context: Dermatan sulfate is one of the two core glycosaminoglycan substrates stored in MPS I-Hurler.

Pathograph Readouts

Readout Of Dermatan sulfate and heparan sulfate accumulation Positive Diagnostic

Increased dermatan sulfate reports the substrate-storage branch downstream of IDUA deficiency.

Show evidence (1 reference)

PMID:32780955 SUPPORT Human Clinical

"Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder, caused by deficiency of α-L-iduronidase, and consequent accumulation of dermatan and heparan sulfates."

This directly identifies dermatan sulfate accumulation in MPS I.

Heparan sulfate (INCREASED)

Context: Heparan sulfate is one of the two core glycosaminoglycan substrates stored in MPS I-Hurler and is relevant to the CNS branch of severe disease.

Pathograph Readouts

Readout Of Dermatan sulfate and heparan sulfate accumulation Positive Diagnostic

Increased heparan sulfate reports the substrate-storage branch downstream of IDUA deficiency.

Readout Of CNS glycosaminoglycan storage injury Positive Diagnostic

Heparan-sulfate storage helps distinguish the severe CNS-involved branch of MPS I.

Show evidence (1 reference)

PMID:32780955 SUPPORT Human Clinical

"Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder, caused by deficiency of α-L-iduronidase, and consequent accumulation of dermatan and heparan sulfates."

This directly identifies heparan sulfate accumulation in MPS I.

Urinary glycosaminoglycans (INCREASED)

Context: Urinary glycosaminoglycan testing reflects tissue GAG storage and is used as part of MPS biochemical evaluation.

Pathograph Readouts

Readout Of Dermatan sulfate and heparan sulfate accumulation Positive Diagnostic

Increased urinary glycosaminoglycans report the systemic substrate-storage mechanism.

Show evidence (2 references)

PMID:28595941 SUPPORT Human Clinical

"Accumulated GAGs of various tissues and their ECM are secreted into the blood circulation and then excreted in urine."

This supports urinary GAGs as a biochemical readout of tissue glycosaminoglycan accumulation.

PMID:28595941 SUPPORT Human Clinical

"The general diagnosis was made by elevated urinary GAGs and/or enzyme assay in serum, leukocytes, and/or fibroblasts."

This explicitly supports elevated urinary GAGs as a diagnostic biochemical readout in mucopolysaccharidoses, including MPS I-Hurler when paired with the disease-specific DS/HS storage evidence.

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Differential Diagnoses

2

Conditions with similar clinical presentations that must be differentiated from Hurler syndrome:

Hurler-Scheie syndrome Not Yet Curated MONDO:0011759

Overlapping Features Hurler-Scheie syndrome is an attenuated MPS I phenotype that overlaps with Hurler syndrome through IDUA deficiency and glycosaminoglycan storage but usually has less severe neurologic involvement and slower progression.

Distinguishing Features

Minimal or delayed central nervous system involvement favors Hurler-Scheie syndrome.
Very early infancy-onset multisystem disease with severe neurodevelopmental risk favors Hurler syndrome.

Show evidence (1 reference)

PMID:28193245 SUPPORT Human Clinical

"However, diagnostic tests for MPS I are of limited value in predicting whether a child will develop severe central nervous system disease associated with Hurler syndrome, or minimal or no central nervous system involvement associated with the attenuated phenotypes (Hurler-Scheie and Scheie syndromes)."

This explicitly distinguishes severe Hurler syndrome from the attenuated Hurler-Scheie phenotype based on CNS involvement.

Scheie syndrome Not Yet Curated MONDO:0011760

Overlapping Features Scheie syndrome is the mildest MPS I phenotype and should be distinguished from Hurler syndrome by its attenuated course and relative absence of early severe neurodevelopmental disease.

Distinguishing Features

Attenuated somatic disease with minimal or no CNS involvement favors Scheie syndrome.
Infantile onset with rapid multisystem progression favors Hurler syndrome.

Show evidence (1 reference)

PMID:28193245 SUPPORT Human Clinical

"However, diagnostic tests for MPS I are of limited value in predicting whether a child will develop severe central nervous system disease associated with Hurler syndrome, or minimal or no central nervous system involvement associated with the attenuated phenotypes (Hurler-Scheie and Scheie syndromes)."

This abstract directly identifies Scheie syndrome as an attenuated MPS I phenotype that must be distinguished from Hurler syndrome.

{ }

Source YAML

click to show

name: Hurler syndrome
creation_date: '2026-04-11T17:12:00Z'
category: Mendelian
description: >-
  Hurler syndrome, also called mucopolysaccharidosis type I-Hurler (MPS-IH), is
  the severe end of the mucopolysaccharidosis type I spectrum. Biallelic loss of
  IDUA activity blocks lysosomal degradation of dermatan sulfate and heparan
  sulfate, causing progressive multisystem glycosaminoglycan storage. The
  disease presents in infancy with coarse facial features, corneal clouding,
  hepatosplenomegaly, skeletal dysplasia, growth failure, joint restriction,
  cardiac disease, and progressive neurodevelopmental involvement. Untreated
  patients typically die in childhood.
classifications:
  lysosomal_storage_category:
    classification_value: mucopolysaccharidosis
    notes: >-
      Hurler syndrome (MPS I) is a mucopolysaccharidosis — lysosomal
      accumulation of the glycosaminoglycans dermatan sulfate and heparan
      sulfate. Complements the ICIMD complex-molecule-degradation axis below.
  icimd_category:
  - classification_value: glycosaminoglycan_degradation
    notes: >-
      ICIMD (Ferreira et al. 2021, PMID:33340416): group "Glycosaminoglycan
      degradation" under category "Disorders of complex molecule degradation".
      Hurler syndrome (MPS I) is alpha-L-iduronidase deficiency.
  isds_skeletal_category:
  - classification_value: lysosomal_storage_with_skeletal_involvement
    notes: >-
      ISDS Nosology and Classification of Genetic Skeletal Disorders, 2019
      revision (Mortier et al., PMID:31633310), Table 1 group 27 "Lysosomal
      storage diseases with skeletal involvement (dysostosis multiplex group)";
      listed as "Mucopolysaccharidosis type 1H-1S".
disease_term:
  preferred_term: Hurler syndrome
  term:
    id: MONDO:0011758
    label: Hurler syndrome
mappings:
  mondo_mappings:
  - term:
      id: MONDO:0011758
      label: Hurler syndrome
    mapping_predicate: skos:exactMatch
    mapping_source: MONDO
parents:
- Mucopolysaccharidosis
- Lysosomal storage disorder
synonyms:
- mucopolysaccharidosis type I-Hurler syndrome
- MPS-IH
- severe mucopolysaccharidosis type I
inheritance:
- name: Autosomal recessive inheritance
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    Hurler syndrome is the severe autosomal recessive form of mucopolysaccharidosis
    type I caused by biallelic pathogenic variants in IDUA.
  evidence:
  - reference: PMID:32780955
    reference_title: "Dysostosis Multiplex in Human Mucopolysaccharidosis Type 1 H and in Animal Models of the Disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder, caused by deficiency of α-L-iduronidase, and consequent accumulation of dermatan and heparan sulfates.
    explanation: >-
      This directly supports autosomal recessive inheritance for severe MPS I,
      the Hurler phenotype.
mechanistic_hypotheses:
- hypothesis_group_id: canonical_idua_deficiency_gag_lysosomal_storage_model
  hypothesis_label: Canonical IDUA Deficiency / Glycosaminoglycan Lysosomal Storage Model
  status: CANONICAL
  description: >-
    Mucopolysaccharidosis type I — Hurler syndrome (severe), Hurler-Scheie (intermediate), and Scheie
    (attenuated) — is an autosomal recessive lysosomal storage disorder caused by loss-of-function
    variants in IDUA encoding α-L-iduronidase. Loss of α-L-iduronidase activity prevents lysosomal
    degradation of heparan sulfate and dermatan sulfate, producing pathological GAG accumulation in
    lysosomes of multiple cell types. Substrate storage drives progressive coarsening, dysostosis
    multiplex, hepatosplenomegaly, cardiac valvular and myocardial disease, corneal clouding, recurrent
    airway obstruction, and (in severe Hurler) progressive neurodevelopmental regression. Hematopoietic
    stem cell transplantation (the standard of care for severe Hurler before age 2), enzyme replacement
    therapy (laronidase), and emerging gene therapy approaches corroborate the IDUA-deficiency / GAG-accumulation
    axis as the canonical pathogenic mechanism.
  notes: >-
    Retained as CANONICAL with an expansion to include secondary cascades. The
    2026 openscientist hypothesis-search report
    (kb/hypotheses/Hurler_syndrome/canonical_idua_deficiency_gag_lysosomal_storage_model)
    finds the model strongly supported; see the assessment sidecar
    assessments/openscientist-assessment-by-claude-opus-5.yaml for the
    claim-by-claim disposition. IDUA deficiency is the necessary upstream
    cause: residual enzyme activity maps quantitatively to clinical severity
    (Hurler 0.18%, Hurler-Scheie 0.27%, Scheie 0.79% of normal in patient
    fibroblasts); laronidase reduces urinary GAGs by about 65% over 26 weeks;
    normal post-HCT enzyme levels predict superior long-term outcomes across
    organ systems (n=217 multicenter); and homozygous IDUA pseudodeficiency
    alleles produce no clinically relevant excess of MPS I features in 1,803
    adults. Critical refinement: GAG accumulation alone is necessary but NOT
    sufficient for the full clinical phenotype. Secondary cascades appear
    integral to pathogenesis: (1) an immune contribution to cardiovascular
    disease, shown in mice as inflammasome upregulation with medial macrophage
    and adventitial T-cell infiltration of the ascending aorta in
    immunocompetent but not immunodeficient MPS I animals, with the human
    counterpart untested (see the HUMAN_MODEL_MISMATCH discussion);
    (2) neuroinflammation with microglial activation and cytokine release;
    (3) cathepsin B leakage from destabilized lysosomes; (4) secondary
    ganglioside accumulation; (5) oxidative stress and mitochondrial
    dysfunction; and (6) disrupted signaling by extracellular
    glycosaminoglycan (FGF and Wnt pathway interactions). Residual disease
    burden persists after successful enzyme correction, but whether that
    reflects self-sustaining secondary cascades or irreversible pre-treatment
    damage plus poor enzyme delivery to avascular tissue is unresolved (see the
    KNOWLEDGE_GAP discussion). HCT (severe Hurler), ERT (laronidase, all
    subtypes), and investigational AAV-IDUA gene therapy validate the canonical
    upstream axis. Three numbers or attributions that appeared in an earlier
    version of this note were provider inference rather than source content and
    have been removed: a ">1.8% residual activity" pseudodeficiency cut-off,
    mast-cell activation as the immune mechanism in valves and myocardium, and
    IGF and BMP as the disrupted growth-factor pathways.
  evidence:
  - reference: PMID:32780955
    reference_title: "Dysostosis Multiplex in Human Mucopolysaccharidosis Type 1 H and in Animal Models of the Disease."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder, caused by deficiency of α-L-iduronidase, and consequent accumulation of dermatan and heparan sulfates."
    explanation: >
      Existing canonical mechanism citation in the dismech
      knowledge base, used as the seed for the hypothesis-search
      deep-research run.
  - reference: PMID:23786846
    reference_title: "Residual α-L-iduronidase activity in fibroblasts of mild to severe Mucopolysaccharidosis type I patients."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Mean residual IDUA activity was 0.18% (range 0-0.6) of the control value in MPS IH fibroblasts (n=5); against 0.27% (range 0.2-0.3) in MPS IH/S cells (n=3); and 0.79% (range 0.3-1.8) in MPS IS fibroblasts (n=5).
    explanation: >-
      Residual alpha-L-iduronidase activity measured in patient fibroblasts
      tracks MPS I subtype severity, with Hurler at the lowest end of the
      gradient. This is the quantitative support for the enzyme-deficiency axis
      of the hypothesis. The series is small (13 cell lines in total) and its
      authors present it as a phenotype-prediction aid rather than as a
      threshold.
  - reference: PMID:39559959
    reference_title: "Long-Term Health Outcomes of Individuals With Pseudodeficiency Alleles in IDUA May Inform Newborn Screening Practices for Mucopolysaccharidosis Type I."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We found no clinically relevant significant differences between cases and controls nor genotype-phenotype associations across four alleles.
    explanation: >-
      Adults homozygous for IDUA pseudodeficiency alleles, which lower in vitro
      enzyme activity without abolishing it, show no excess of MPS I features
      against matched controls. This supports severe loss of
      alpha-L-iduronidase activity, rather than any reduction, as the
      requirement for disease. Ascertainment is by electronic medical record
      within a hospital biorepository, and the study reports no enzyme activity
      values.
pathophysiology:
- name: IDUA enzyme deficiency
  description: >-
    Hurler syndrome results from severe alpha-L-iduronidase deficiency caused by
    biallelic loss of IDUA function.
  gene:
    preferred_term: IDUA
    description: Encodes alpha-L-iduronidase, the lysosomal enzyme deficient in Hurler syndrome.
    modifier: ABNORMAL
    term:
      id: hgnc:5391
      label: IDUA
  genes:
  - preferred_term: IDUA
    term:
      id: hgnc:5391
      label: IDUA
  molecular_functions:
  - preferred_term: alpha-L-iduronidase activity
    modifier: DECREASED
    term:
      id: GO:0003940
      label: L-iduronidase activity
  biological_processes:
  - preferred_term: glycosaminoglycan catabolic process
    modifier: DECREASED
    term:
      id: GO:0006027
      label: glycosaminoglycan catabolic process
  evidence:
  - reference: PMID:32780955
    reference_title: "Dysostosis Multiplex in Human Mucopolysaccharidosis Type 1 H and in Animal Models of the Disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder, caused by deficiency of α-L-iduronidase, and consequent accumulation of dermatan and heparan sulfates.
    explanation: >-
      This directly states the core alpha-L-iduronidase enzyme deficiency in
      Hurler syndrome.
  downstream:
  - target: Dermatan sulfate and heparan sulfate accumulation
    description: Loss of alpha-L-iduronidase blocks lysosomal clearance of dermatan sulfate and heparan sulfate
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:32780955
      reference_title: "Dysostosis Multiplex in Human Mucopolysaccharidosis Type 1 H and in Animal Models of the Disease."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder, caused by deficiency of α-L-iduronidase, and consequent accumulation of dermatan and heparan sulfates.
      explanation: >-
        This directly links alpha-L-iduronidase deficiency to dermatan sulfate
        and heparan sulfate accumulation.
  - target: Alpha-L-iduronidase activity
    description: Severe IDUA loss is directly reflected by deficient alpha-L-iduronidase enzyme activity.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:32780955
      reference_title: "Dysostosis Multiplex in Human Mucopolysaccharidosis Type 1 H and in Animal Models of the Disease."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder, caused by deficiency of α-L-iduronidase, and consequent accumulation of dermatan and heparan sulfates.
      explanation: >-
        This supports low alpha-L-iduronidase activity as the direct biochemical
        readout of IDUA enzyme deficiency.
- name: Dermatan sulfate and heparan sulfate accumulation
  conforms_to: "lysosomal_substrate_accumulation#Lysosomal Substrate Accumulation"
  description: >-
    Loss of IDUA blocks lysosomal degradation of dermatan sulfate and heparan
    sulfate, causing progressive glycosaminoglycan storage in cells and
    connective tissues.
  cellular_components:
  - preferred_term: lysosome
    term:
      id: GO:0005764
      label: lysosome
  chemical_entities:
  - preferred_term: dermatan sulfate
    term:
      id: CHEBI:18376
      label: dermatan sulfate
    modifier: INCREASED
  - preferred_term: heparan sulfate
    term:
      id: CHEBI:28815
      label: heparan sulfate
    modifier: INCREASED
  - preferred_term: glycosaminoglycan
    term:
      id: CHEBI:18085
      label: glycosaminoglycan
    modifier: INCREASED
  evidence:
  - reference: PMID:32780955
    reference_title: "Dysostosis Multiplex in Human Mucopolysaccharidosis Type 1 H and in Animal Models of the Disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder, caused by deficiency of α-L-iduronidase, and consequent accumulation of dermatan and heparan sulfates.
    explanation: >-
      This directly supports dermatan sulfate and heparan sulfate accumulation
      as the immediate biochemical consequence of IDUA deficiency.
  - reference: PMID:28595941
    reference_title: "Epidemiology of mucopolysaccharidoses."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      MPS I with either severe or attenuated form has limited activity of the enzyme α-L-iduronidase (IDUA) that breaks down DS and HS. These GAGs remain stored in cells causing progressive damage of various tissues including bone and, in severe cases, brain.
    explanation: >-
      This supports persistent DS and HS storage as the central substrate
      accumulation mechanism in severe MPS I.
  downstream:
  - target: Progressive skeletal and multisystem organ injury
    description: Glycosaminoglycan storage drives progressive skeletal, visceral, cardiac, and CNS injury
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:28595941
      reference_title: "Epidemiology of mucopolysaccharidoses."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        MPS I with either severe or attenuated form has limited activity of the enzyme α-L-iduronidase (IDUA) that breaks down DS and HS. These GAGs remain stored in cells causing progressive damage of various tissues including bone and, in severe cases, brain.
      explanation: >-
        The review explicitly links DS and HS storage to progressive tissue
        damage in bone and brain.
  - target: CNS glycosaminoglycan storage injury
    description: Heparan-sulfate-containing storage disease contributes to severe CNS involvement in Hurler syndrome.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:28595941
      reference_title: "Epidemiology of mucopolysaccharidoses."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        These GAGs remain stored in cells causing progressive damage of various tissues including bone and, in severe cases, brain.
      explanation: >-
        This directly supports a severe-MPS-I brain-injury branch downstream of
        glycosaminoglycan storage.
  - target: Dermatan sulfate
    description: Dermatan sulfate accumulation is one of the core stored substrates in MPS I.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:32780955
      reference_title: "Dysostosis Multiplex in Human Mucopolysaccharidosis Type 1 H and in Animal Models of the Disease."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder, caused by deficiency of α-L-iduronidase, and consequent accumulation of dermatan and heparan sulfates.
      explanation: >-
        This supports dermatan sulfate as a direct stored biochemical substrate.
  - target: Heparan sulfate
    description: Heparan sulfate accumulation is one of the core stored substrates in MPS I.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:32780955
      reference_title: "Dysostosis Multiplex in Human Mucopolysaccharidosis Type 1 H and in Animal Models of the Disease."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder, caused by deficiency of α-L-iduronidase, and consequent accumulation of dermatan and heparan sulfates.
      explanation: >-
        This supports heparan sulfate as a direct stored biochemical substrate.
  - target: Urinary glycosaminoglycans
    description: Cellular glycosaminoglycan storage is reflected by abnormal urinary GAG excretion.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - accumulated GAGs secreted into blood and excreted in urine
    evidence:
    - reference: PMID:28595941
      reference_title: "Epidemiology of mucopolysaccharidoses."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Accumulated GAGs of various tissues and their ECM are secreted into the blood circulation and then excreted in urine.
      explanation: >-
        This supports urinary glycosaminoglycans as a downstream readout of
        tissue glycosaminoglycan storage.
- name: CNS glycosaminoglycan storage injury
  conforms_to: "mps_gag_storage#Heparan Sulfate-Driven Neuroinflammation"
  description: >-
    In severe MPS I, glycosaminoglycan storage extends to the brain and drives
    the Hurler neurologic branch, including early developmental delay and
    enlarged head circumference.
  cellular_components:
  - preferred_term: lysosome
    term:
      id: GO:0005764
      label: lysosome
  chemical_entities:
  - preferred_term: heparan sulfate
    term:
      id: CHEBI:28815
      label: heparan sulfate
    modifier: INCREASED
  - preferred_term: glycosaminoglycan
    term:
      id: CHEBI:18085
      label: glycosaminoglycan
    modifier: INCREASED
  evidence:
  - reference: PMID:28595941
    reference_title: "Epidemiology of mucopolysaccharidoses."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These GAGs remain stored in cells causing progressive damage of various tissues including bone and, in severe cases, brain.
    explanation: >-
      This directly supports brain involvement from glycosaminoglycan storage in
      severe MPS I.
  downstream:
  - target: Global developmental delay
    causal_link_type: DIRECT
    description: Severe CNS storage involvement contributes to early developmental delay.
    evidence:
    - reference: PMID:28595941
      reference_title: "Epidemiology of mucopolysaccharidoses."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Patients with Hurler syndrome develop initial symptoms like hernias, hepatomegaly, kyphosis and developmental delay within a year and die within a decade if untreated
      explanation: >-
        This directly supports early developmental delay in severe Hurler
        syndrome.
  - target: Macrocephaly
    causal_link_type: DIRECT
    description: Severe early Hurler involvement includes enlarged head circumference.
    evidence:
    - reference: PMID:28193245
      reference_title: "Early disease progression of Hurler syndrome."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Other symptoms such as kyphosis, corneal clouding, cardiac disease, joint restrictions, and enlarged head circumference typically appeared slightly later (median age, 8-10 months).
      explanation: >-
        Enlarged head circumference supports macrocephaly as part of the early
        severe Hurler phenotype.
- name: Progressive skeletal and multisystem organ injury
  conforms_to: "mps_gag_storage#Multisystem Somatic Disease"
  description: >-
    Glycosaminoglycan storage in connective tissues drives progressive
    dysostosis multiplex, kyphosis, joint restriction, organomegaly, ocular
    disease, and cardiac involvement beginning in infancy. In severe Hurler
    syndrome, clinical signs emerge within the first months of life and the
    disease progresses rapidly.
  cell_types:
  - preferred_term: chondrocyte
    term:
      id: CL:0000138
      label: chondrocyte
  evidence:
  - reference: PMID:32780955
    reference_title: "Dysostosis Multiplex in Human Mucopolysaccharidosis Type 1 H and in Animal Models of the Disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A prominent clinical manifestation of MPS-IH is dysostosis multiplex, a constellation of skeletal abnormalities.
    explanation: >-
      This supports severe skeletal tissue involvement as a central downstream
      consequence of Hurler pathophysiology.
  - reference: PMID:28193245
    reference_title: "Early disease progression of Hurler syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Nearly all patients (98%) showed signs of disease during the first 6 months of life.
    explanation: >-
      This infant cohort directly supports the rapid early multisystem
      progression characteristic of Hurler syndrome.
  downstream:
  - target: Dysostosis multiplex
    causal_link_type: DIRECT
    description: Skeletal glycosaminoglycan storage manifests as dysostosis multiplex in severe MPS I.
    evidence:
    - reference: PMID:32780955
      reference_title: "Dysostosis Multiplex in Human Mucopolysaccharidosis Type 1 H and in Animal Models of the Disease."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        A prominent clinical manifestation of MPS-IH is dysostosis multiplex, a constellation of skeletal abnormalities.
      explanation: >-
        This directly connects the skeletal injury branch to dysostosis
        multiplex.
  - target: Coarse facial features
    causal_link_type: DIRECT
    description: Multisystem storage disease includes progressive coarse facial morphology.
    evidence:
    - reference: PMID:28595941
      reference_title: "Epidemiology of mucopolysaccharidoses."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Typical manifestations include coarse face, corneal clouding, developmental delay, mental retardation, growth retardation, contractures of the joints, kyphoscoliosis, dysostosis multiplex, hearing loss, thickening of the heart valves, hepatosplenomegaly, and umbilical and inguinal hernias.
      explanation: >-
        This lists coarse face among the typical manifestations downstream of
        severe MPS I storage disease.
  - target: Corneal opacity
    causal_link_type: DIRECT
    description: Ocular storage involvement manifests clinically as corneal clouding.
    evidence:
    - reference: PMID:28193245
      reference_title: "Early disease progression of Hurler syndrome."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Other symptoms such as kyphosis, corneal clouding, cardiac disease, joint restrictions, and enlarged head circumference typically appeared slightly later (median age, 8-10 months).
      explanation: >-
        The Hurler natural-history cohort documents corneal clouding as an
        early storage-related manifestation.
  - target: Hearing impairment
    causal_link_type: DIRECT
    description: Otolaryngologic involvement in Hurler syndrome includes hearing loss.
    evidence:
    - reference: PMID:28595941
      reference_title: "Epidemiology of mucopolysaccharidoses."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Typical manifestations include coarse face, corneal clouding, developmental delay, mental retardation, growth retardation, contractures of the joints, kyphoscoliosis, dysostosis multiplex, hearing loss, thickening of the heart valves, hepatosplenomegaly, and umbilical and inguinal hernias.
      explanation: >-
        This identifies hearing loss as part of the clinical manifestation set
        for severe MPS I.
  - target: Hepatosplenomegaly
    causal_link_type: DIRECT
    description: Visceral storage involvement causes liver and spleen enlargement.
    evidence:
    - reference: PMID:28595941
      reference_title: "Epidemiology of mucopolysaccharidoses."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Typical manifestations include coarse face, corneal clouding, developmental delay, mental retardation, growth retardation, contractures of the joints, kyphoscoliosis, dysostosis multiplex, hearing loss, thickening of the heart valves, hepatosplenomegaly, and umbilical and inguinal hernias.
      explanation: >-
        This lists hepatosplenomegaly among the typical severe MPS I
        manifestations.
  - target: Global developmental delay
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Brain glycosaminoglycan storage and severe CNS involvement disrupt early neurodevelopment.
    description: Severe CNS involvement in Hurler syndrome contributes to early developmental delay.
    evidence:
    - reference: PMID:28595941
      reference_title: "Epidemiology of mucopolysaccharidoses."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Patients with Hurler syndrome develop initial symptoms like hernias, hepatomegaly, kyphosis and developmental delay within a year and die within a decade if untreated
      explanation: >-
        This disease-specific summary connects early severe Hurler disease to
        developmental delay.
  - target: Joint stiffness
    causal_link_type: DIRECT
    description: Connective-tissue storage manifests as early joint restriction and stiffness.
    evidence:
    - reference: PMID:28193245
      reference_title: "Early disease progression of Hurler syndrome."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Other symptoms such as kyphosis, corneal clouding, cardiac disease, joint restrictions, and enlarged head circumference typically appeared slightly later (median age, 8-10 months).
      explanation: >-
        Joint restrictions are close clinical support for the joint stiffness
        endpoint term.
  - target: Abnormal heart valve morphology
    causal_link_type: DIRECT
    description: Cardiac storage involvement includes thickening of the heart valves.
    evidence:
    - reference: PMID:28595941
      reference_title: "Epidemiology of mucopolysaccharidoses."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Typical manifestations include coarse face, corneal clouding, developmental delay, mental retardation, growth retardation, contractures of the joints, kyphoscoliosis, dysostosis multiplex, hearing loss, thickening of the heart valves, hepatosplenomegaly, and umbilical and inguinal hernias.
      explanation: >-
        This directly supports heart-valve thickening as a downstream cardiac
        manifestation.
  - target: Growth delay
    causal_link_type: DIRECT
    description: Severe somatic storage disease includes impaired growth.
    evidence:
    - reference: PMID:28595941
      reference_title: "Epidemiology of mucopolysaccharidoses."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Typical manifestations include coarse face, corneal clouding, developmental delay, mental retardation, growth retardation, contractures of the joints, kyphoscoliosis, dysostosis multiplex, hearing loss, thickening of the heart valves, hepatosplenomegaly, and umbilical and inguinal hernias.
      explanation: >-
        This identifies growth retardation as a typical severe MPS I
        manifestation.
  - target: Kyphosis
    causal_link_type: DIRECT
    description: Skeletal storage disease includes early kyphosis.
    evidence:
    - reference: PMID:28595941
      reference_title: "Epidemiology of mucopolysaccharidoses."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Patients with Hurler syndrome develop initial symptoms like hernias, hepatomegaly, kyphosis and developmental delay within a year and die within a decade if untreated
      explanation: >-
        This disease-specific statement lists kyphosis among initial Hurler
        symptoms.
  - target: Umbilical hernia
    causal_link_type: DIRECT
    description: Connective-tissue and abdominal-wall involvement includes umbilical hernia.
    evidence:
    - reference: PMID:28595941
      reference_title: "Epidemiology of mucopolysaccharidoses."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Typical manifestations include coarse face, corneal clouding, developmental delay, mental retardation, growth retardation, contractures of the joints, kyphoscoliosis, dysostosis multiplex, hearing loss, thickening of the heart valves, hepatosplenomegaly, and umbilical and inguinal hernias.
      explanation: >-
        This directly lists umbilical hernia as part of the typical severe MPS I
        manifestation set.
  - target: Inguinal hernia
    causal_link_type: DIRECT
    description: Connective-tissue and abdominal-wall involvement includes inguinal hernia.
    evidence:
    - reference: PMID:28595941
      reference_title: "Epidemiology of mucopolysaccharidoses."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Typical manifestations include coarse face, corneal clouding, developmental delay, mental retardation, growth retardation, contractures of the joints, kyphoscoliosis, dysostosis multiplex, hearing loss, thickening of the heart valves, hepatosplenomegaly, and umbilical and inguinal hernias.
      explanation: >-
        This directly lists inguinal hernia as part of the typical severe MPS I
        manifestation set.
  - target: Recurrent otitis media
    causal_link_type: DIRECT
    description: Early otolaryngologic involvement includes otitis media.
    evidence:
    - reference: PMID:28193245
      reference_title: "Early disease progression of Hurler syndrome."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Common early disease manifestations included failed newborn hearing screen, respiratory symptoms, difficulty latching, and otitis media.
      explanation: >-
        This natural-history cohort identifies otitis media as a common early
        Hurler manifestation; PARTIAL because the snippet documents otitis media
        but does not explicitly quantify the recurrence in the HP term.
  - target: Recurrent respiratory infections
    causal_link_type: DIRECT
    description: Early upper-airway and respiratory involvement includes frequent respiratory infections.
    evidence:
    - reference: PMID:20301341
      reference_title: Mucopolysaccharidosis Type I.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Typical early manifestations are nonspecific (e.g., umbilical or inguinal hernia, frequent upper respiratory tract infections before age 1 year).
      explanation: >-
        GeneReviews identifies frequent upper respiratory tract infections as a
        typical early manifestation of severe MPS I.
  - target: Obstructive Sleep Apnea / Upper Airway Obstruction
    causal_link_type: DIRECT
    description: >-
      Multisystem respiratory involvement in MPS I includes upper-airway
      obstruction and obstructive sleep apnea.
    evidence:
    - reference: PMID:20301341
      reference_title: Mucopolysaccharidosis Type I.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        tonsillectomy and adenoidectomy for eustachian tube dysfunction and/or upper airway obstruction; ventilating tubes; hearing aids as needed; CPAP for sleep apnea
      explanation: >-
        GeneReviews lists upper-airway obstruction and CPAP-managed sleep apnea
        in the MPS I supportive-care section, supporting this respiratory
        phenotype as a downstream manifestation of the multisystem disease.
phenotypes:
- name: Obstructive Sleep Apnea / Upper Airway Obstruction
  category: Respiratory
  description: >-
    GAG deposition in adenoids, tonsils, soft palate, tongue, and tracheo-bronchial
    cartilage produces upper-airway obstruction and obstructive
    sleep apnea, which is a common cause of morbidity in untreated MPS I.
    Tonsillectomy/adenoidectomy and CPAP are standard interventions.
  phenotype_term:
    preferred_term: Obstructive sleep apnea
    term:
      id: HP:0002870
      label: Obstructive sleep apnea
  evidence:
  - reference: PMID:20301341
    reference_title: Mucopolysaccharidosis Type I.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "tonsillectomy and adenoidectomy for eustachian tube dysfunction and/or upper airway obstruction; ventilating tubes; hearing aids as needed; CPAP for sleep apnea"
    explanation: >-
      GeneReviews documents CPAP for sleep apnea (alongside tonsillectomy/
      adenoidectomy for upper-airway obstruction) in MPS I, directly naming the
      obstructive sleep apnea phenotype.
- name: Dysostosis multiplex
  category: Skeletal
  description: >-
    Severe skeletal dysplasia with dysostosis multiplex is a hallmark feature of
    Hurler syndrome.
  phenotype_term:
    preferred_term: Dysostosis multiplex
    term:
      id: HP:0000943
      label: Dysostosis multiplex
  evidence:
  - reference: PMID:32780955
    reference_title: "Dysostosis Multiplex in Human Mucopolysaccharidosis Type 1 H and in Animal Models of the Disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A prominent clinical manifestation of MPS-IH is dysostosis multiplex, a constellation of skeletal abnormalities.
    explanation: >-
      This directly identifies dysostosis multiplex as a prominent Hurler
      phenotype.
- name: Coarse facial features
  category: Craniofacial
  frequency: VERY_FREQUENT
  description: >-
    Progressive coarsening of the face is a characteristic somatic feature of
    Hurler syndrome.
  phenotype_term:
    preferred_term: Coarse facial features
    term:
      id: HP:0000280
      label: Coarse facial features
  evidence:
  - reference: PMID:28595941
    reference_title: "Epidemiology of mucopolysaccharidoses."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Typical manifestations include coarse face, corneal clouding, developmental delay, mental retardation, growth retardation, contractures of the joints, kyphoscoliosis, dysostosis multiplex, hearing loss, thickening of the heart valves, hepatosplenomegaly, and umbilical and inguinal hernias.
    explanation: >-
      This review explicitly lists coarse facial appearance among the typical
      manifestations of severe MPS I.
  - reference: ORPHA:93473
    reference_title: "Hurler syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0000280 | Coarse facial features | Very frequent (99-80%)"
    explanation: >-
      Orphanet records coarse facial features as very frequent in Hurler
      syndrome, supporting the VERY_FREQUENT frequency band.
- name: Corneal opacity
  category: Ophthalmic
  description: >-
    Corneal clouding appears early in infancy and is a classic ocular feature of
    Hurler syndrome. Morphologic work in MPS animal models locates the lesion in
    glycosaminoglycan-laden stromal keratocytes rather than in endothelial
    decompensation: the MPS I corneal endothelium carries abundant lysosomal
    inclusions yet still maintains corneal dehydration normally.
  phenotype_term:
    preferred_term: Corneal opacity
    term:
      id: HP:0007957
      label: Corneal opacity
  evidence:
  - reference: PMID:28193245
    reference_title: "Early disease progression of Hurler syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Other symptoms such as kyphosis, corneal clouding, cardiac disease, joint restrictions, and enlarged head circumference typically appeared slightly later (median age, 8-10 months).
    explanation: >-
      The infant natural-history cohort directly documents corneal clouding as
      an early Hurler manifestation.
  - reference: PMID:8907377
    reference_title: "Corneal endothelium in mucopolysaccharide storage disorders. Morphologic studies in animal models."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      The corneal clouding was the result of storage in stromal keratocytes rather than corneal edema from endothelial dysfunction.
    explanation: >-
      Morphologic study of MPS I cat, MPS VI cat, and MPS VII dog corneas
      locates the lesion in stromal keratocytes. MPS I endothelium carried
      abundant lysosomal inclusions yet still maintained corneal dehydration
      normally, so the clouding is a stromal storage lesion rather than
      endothelial decompensation. This grounds the cellular substrate of the
      phenotype; it is animal morphology and does not by itself speak to the
      human frequency or course.
- name: Hearing impairment
  category: Otolaryngologic
  description: >-
    Auditory involvement begins early in Hurler syndrome and may be evident from
    an abnormal newborn hearing screen in infancy.
  phenotype_term:
    preferred_term: Hearing impairment
    term:
      id: HP:0000365
      label: Hearing impairment
  evidence:
  - reference: PMID:28193245
    reference_title: "Early disease progression of Hurler syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Common early disease manifestations included failed newborn hearing screen, respiratory symptoms, difficulty latching, and otitis media.
    explanation: >-
      Failed newborn hearing screening is partial but clinically meaningful
      support for early hearing impairment in Hurler syndrome.
- name: Hepatosplenomegaly
  category: Gastrointestinal
  description: >-
    Liver and spleen enlargement are common visceral manifestations of Hurler
    syndrome.
  phenotype_term:
    preferred_term: Hepatosplenomegaly
    term:
      id: HP:0001433
      label: Hepatosplenomegaly
  evidence:
  - reference: PMID:28595941
    reference_title: "Epidemiology of mucopolysaccharidoses."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Typical manifestations include coarse face, corneal clouding, developmental delay, mental retardation, growth retardation, contractures of the joints, kyphoscoliosis, dysostosis multiplex, hearing loss, thickening of the heart valves, hepatosplenomegaly, and umbilical and inguinal hernias.
    explanation: >-
      This directly lists hepatosplenomegaly among typical severe MPS I
      manifestations.
- name: Global developmental delay
  category: Neurologic
  description: >-
    Severe MPS I causes early neurodevelopmental impairment with progressive CNS
    involvement if untreated.
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:28595941
    reference_title: "Epidemiology of mucopolysaccharidoses."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Patients with Hurler syndrome develop initial symptoms like hernias, hepatomegaly, kyphosis and developmental delay within a year and die within a decade if untreated
    explanation: >-
      This directly documents developmental delay as an early severe Hurler
      manifestation.
- name: Joint stiffness
  category: Musculoskeletal
  description: >-
    Progressive joint restriction reflects connective-tissue glycosaminoglycan
    storage in Hurler syndrome.
  phenotype_term:
    preferred_term: Joint stiffness
    term:
      id: HP:0001387
      label: Joint stiffness
  evidence:
  - reference: PMID:28193245
    reference_title: "Early disease progression of Hurler syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Other symptoms such as kyphosis, corneal clouding, cardiac disease, joint restrictions, and enlarged head circumference typically appeared slightly later (median age, 8-10 months).
    explanation: >-
      The abstract reports joint restrictions rather than the exact ontology
      wording, so this is partial support for the closely related phenotype of
      joint stiffness.
- name: Abnormal heart valve morphology
  category: Cardiac
  description: >-
    Cardiac valve thickening and other cardiac manifestations contribute
    substantially to morbidity in Hurler syndrome.
  phenotype_term:
    preferred_term: Abnormal heart valve morphology
    term:
      id: HP:0001654
      label: Abnormal heart valve morphology
  evidence:
  - reference: PMID:28595941
    reference_title: "Epidemiology of mucopolysaccharidoses."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Typical manifestations include coarse face, corneal clouding, developmental delay, mental retardation, growth retardation, contractures of the joints, kyphoscoliosis, dysostosis multiplex, hearing loss, thickening of the heart valves, hepatosplenomegaly, and umbilical and inguinal hernias.
    explanation: >-
      This specifically identifies heart-valve thickening among the typical
      manifestations of severe MPS I.
- name: Growth delay
  category: Growth
  description: >-
    Progressive growth retardation is part of the severe somatic phenotype of
    Hurler syndrome.
  phenotype_term:
    preferred_term: Growth delay
    term:
      id: HP:0001510
      label: Growth delay
  evidence:
  - reference: PMID:28595941
    reference_title: "Epidemiology of mucopolysaccharidoses."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Typical manifestations include coarse face, corneal clouding, developmental delay, mental retardation, growth retardation, contractures of the joints, kyphoscoliosis, dysostosis multiplex, hearing loss, thickening of the heart valves, hepatosplenomegaly, and umbilical and inguinal hernias.
    explanation: >-
      This directly supports growth retardation as a characteristic Hurler
      phenotype.
- name: Kyphosis
  category: Skeletal
  description: >-
    Kyphosis is an early skeletal manifestation of severe Hurler syndrome.
  phenotype_term:
    preferred_term: Kyphosis
    term:
      id: HP:0002808
      label: Kyphosis
  evidence:
  - reference: PMID:28595941
    reference_title: "Epidemiology of mucopolysaccharidoses."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Patients with Hurler syndrome develop initial symptoms like hernias, hepatomegaly, kyphosis and developmental delay within a year and die within a decade if untreated
    explanation: >-
      This directly identifies kyphosis as an early Hurler manifestation.
- name: Macrocephaly
  category: Neurologic
  description: >-
    Enlarged head circumference appears during infancy in Hurler syndrome.
  phenotype_term:
    preferred_term: Macrocephaly
    term:
      id: HP:0000256
      label: Macrocephaly
  evidence:
  - reference: PMID:28193245
    reference_title: "Early disease progression of Hurler syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Other symptoms such as kyphosis, corneal clouding, cardiac disease, joint restrictions, and enlarged head circumference typically appeared slightly later (median age, 8-10 months).
    explanation: >-
      Enlarged head circumference is direct support for macrocephaly.
- name: Umbilical hernia
  category: Gastrointestinal
  description: >-
    Umbilical hernia is a characteristic abdominal-wall manifestation of severe
    MPS I.
  phenotype_term:
    preferred_term: Umbilical hernia
    term:
      id: HP:0001537
      label: Umbilical hernia
  evidence:
  - reference: PMID:28595941
    reference_title: "Epidemiology of mucopolysaccharidoses."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Typical manifestations include coarse face, corneal clouding, developmental delay, mental retardation, growth retardation, contractures of the joints, kyphoscoliosis, dysostosis multiplex, hearing loss, thickening of the heart valves, hepatosplenomegaly, and umbilical and inguinal hernias.
    explanation: >-
      The review directly lists umbilical hernia among typical severe MPS I
      manifestations.
- name: Inguinal hernia
  category: Gastrointestinal
  description: >-
    Inguinal hernia is a characteristic abdominal-wall manifestation of severe
    MPS I.
  phenotype_term:
    preferred_term: Inguinal hernia
    term:
      id: HP:0000023
      label: Inguinal hernia
  evidence:
  - reference: PMID:28595941
    reference_title: "Epidemiology of mucopolysaccharidoses."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Typical manifestations include coarse face, corneal clouding, developmental delay, mental retardation, growth retardation, contractures of the joints, kyphoscoliosis, dysostosis multiplex, hearing loss, thickening of the heart valves, hepatosplenomegaly, and umbilical and inguinal hernias.
    explanation: >-
      The review directly lists inguinal hernia among typical severe MPS I
      manifestations.
- name: Recurrent otitis media
  category: Otolaryngologic
  description: >-
    Otitis media is a common early otolaryngologic manifestation in Hurler
    syndrome.
  phenotype_term:
    preferred_term: Recurrent otitis media
    term:
      id: HP:0000403
      label: Recurrent otitis media
  evidence:
  - reference: PMID:28193245
    reference_title: "Early disease progression of Hurler syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Common early disease manifestations included failed newborn hearing screen, respiratory symptoms, difficulty latching, and otitis media.
    explanation: >-
      This directly identifies otitis media among common early manifestations;
      PARTIAL because the snippet documents otitis media without explicitly
      establishing the recurrence captured by HP:0000403.
- name: Recurrent respiratory infections
  category: Respiratory
  description: >-
    Frequent upper respiratory tract infections can appear before age one year in
    severe MPS I.
  phenotype_term:
    preferred_term: Recurrent respiratory infections
    term:
      id: HP:0002205
      label: Recurrent respiratory infections
  evidence:
  - reference: PMID:20301341
    reference_title: Mucopolysaccharidosis Type I.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Typical early manifestations are nonspecific (e.g., umbilical or inguinal hernia, frequent upper respiratory tract infections before age 1 year).
    explanation: >-
      This GeneReviews summary directly supports recurrent respiratory
      infections as an early severe MPS I feature.
biochemical:
- name: Alpha-L-iduronidase activity
  presence: DECREASED
  context: >-
    Deficient alpha-L-iduronidase activity is the proximal biochemical defect in
    MPS I-Hurler.
  readouts:
  - target: IDUA enzyme deficiency
    relationship: READOUT_OF
    direction: NEGATIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Low alpha-L-iduronidase enzyme activity directly reports the IDUA loss-of-function mechanism.
  evidence:
  - reference: PMID:32780955
    reference_title: "Dysostosis Multiplex in Human Mucopolysaccharidosis Type 1 H and in Animal Models of the Disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder, caused by deficiency of α-L-iduronidase, and consequent accumulation of dermatan and heparan sulfates.
    explanation: >-
      This directly supports deficient alpha-L-iduronidase as the core
      biochemical abnormality.
- name: Dermatan sulfate
  presence: INCREASED
  context: >-
    Dermatan sulfate is one of the two core glycosaminoglycan substrates stored
    in MPS I-Hurler.
  biomarker_term:
    preferred_term: dermatan sulfate
    term:
      id: CHEBI:18376
      label: dermatan sulfate
  readouts:
  - target: Dermatan sulfate and heparan sulfate accumulation
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Increased dermatan sulfate reports the substrate-storage branch downstream of IDUA deficiency.
  evidence:
  - reference: PMID:32780955
    reference_title: "Dysostosis Multiplex in Human Mucopolysaccharidosis Type 1 H and in Animal Models of the Disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder, caused by deficiency of α-L-iduronidase, and consequent accumulation of dermatan and heparan sulfates.
    explanation: >-
      This directly identifies dermatan sulfate accumulation in MPS I.
- name: Heparan sulfate
  presence: INCREASED
  context: >-
    Heparan sulfate is one of the two core glycosaminoglycan substrates stored
    in MPS I-Hurler and is relevant to the CNS branch of severe disease.
  biomarker_term:
    preferred_term: heparan sulfate
    term:
      id: CHEBI:28815
      label: heparan sulfate
  readouts:
  - target: Dermatan sulfate and heparan sulfate accumulation
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Increased heparan sulfate reports the substrate-storage branch downstream of IDUA deficiency.
  - target: CNS glycosaminoglycan storage injury
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Heparan-sulfate storage helps distinguish the severe CNS-involved branch of MPS I.
  evidence:
  - reference: PMID:32780955
    reference_title: "Dysostosis Multiplex in Human Mucopolysaccharidosis Type 1 H and in Animal Models of the Disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder, caused by deficiency of α-L-iduronidase, and consequent accumulation of dermatan and heparan sulfates.
    explanation: >-
      This directly identifies heparan sulfate accumulation in MPS I.
- name: Urinary glycosaminoglycans
  presence: INCREASED
  context: >-
    Urinary glycosaminoglycan testing reflects tissue GAG storage and is used as
    part of MPS biochemical evaluation.
  biomarker_term:
    preferred_term: glycosaminoglycan
    term:
      id: CHEBI:18085
      label: glycosaminoglycan
  readouts:
  - target: Dermatan sulfate and heparan sulfate accumulation
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Increased urinary glycosaminoglycans report the systemic substrate-storage mechanism.
  evidence:
  - reference: PMID:28595941
    reference_title: "Epidemiology of mucopolysaccharidoses."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Accumulated GAGs of various tissues and their ECM are secreted into the blood circulation and then excreted in urine.
    explanation: >-
      This supports urinary GAGs as a biochemical readout of tissue
      glycosaminoglycan accumulation.
  - reference: PMID:28595941
    reference_title: "Epidemiology of mucopolysaccharidoses."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The general diagnosis was made by elevated urinary GAGs and/or enzyme assay in serum, leukocytes, and/or fibroblasts.
    explanation: >-
      This explicitly supports elevated urinary GAGs as a diagnostic biochemical
      readout in mucopolysaccharidoses, including MPS I-Hurler when paired with
      the disease-specific DS/HS storage evidence.
genetic:
- name: IDUA
  association: Loss-of-function
  gene_term:
    preferred_term: IDUA
    term:
      id: hgnc:5391
      label: IDUA
  notes: >-
    Hurler syndrome is caused by severe biallelic deficiency of alpha-L-iduronidase
    encoded by IDUA. Disease severity reflects the severe end of the MPS I
    spectrum, with marked accumulation of dermatan sulfate and heparan sulfate.
    Common reported IDUA alleles in MPS I include p.W402X and p.Q70X.
  evidence:
  - reference: PMID:32780955
    reference_title: "Dysostosis Multiplex in Human Mucopolysaccharidosis Type 1 H and in Animal Models of the Disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder, caused by deficiency of α-L-iduronidase, and consequent accumulation of dermatan and heparan sulfates.
    explanation: >-
      This establishes alpha-L-iduronidase deficiency, i.e. loss of IDUA
      function, as the primary genetic cause of Hurler syndrome.
  - reference: PMID:28595941
    reference_title: "Epidemiology of mucopolysaccharidoses."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The two most common IDUA mutations are p.W402X and p.Q70X.
    explanation: >-
      This supports noting p.W402X and p.Q70X as common IDUA alleles in MPS I.
  - reference: PMID:31194252
    reference_title: "Genotype-phenotype relationships in mucopolysaccharidosis type I (MPS I): Insights from the International MPS I Registry."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      About 67.6% of severe patients had genotypes where both variants identified are predicted to severely disrupt protein/gene function and 96.1% of attenuated patients had at least one missense or intronic variant.
    explanation: >-
      In 538 registry patients with both IDUA alleles identified, the severe
      (Hurler) end of the spectrum is dominated by genotypes in which neither
      allele can produce functional enzyme, while attenuated disease almost
      always retains a missense or intronic allele. This is the genotype-level
      support for biallelic severe loss of function as the basis of Hurler
      syndrome specifically.
treatments:
- name: AAV-IDUA gene therapy (investigational)
  description: >-
    AAV-mediated IDUA gene therapy is in clinical development for severe
    MPS I. A first-in-human intracisternal AAV9-IDUA case reported
    durable neurodevelopmental benefit with >5-year follow-up. Multiple
    additional gene therapy strategies (intracerebroventricular AAV9,
    ex vivo lentiviral CD34+ HSC IDUA gene transfer) are in trials.
  therapeutic_modality: GENE_THERAPY
  treatment_term:
    preferred_term: gene therapy
    term:
      id: NCIT:C15238
      label: Gene Therapy
  target_mechanisms:
  - target: IDUA enzyme deficiency
    treatment_effect: RESTORES
    description: >-
      AAV-delivered IDUA cDNA expressed in CNS or hematopoietic-progeny
      cells restores α-L-iduronidase activity and supports cross-correction
      of neighboring cells through mannose-6-phosphate receptor uptake.
  evidence:
  - reference: PMID:41966056
    reference_title: "First-in-human intracisternal dosing of RGX-111 in severe MPS I is well tolerated and generates sustained neurodevelopment without HSCT."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Neurocognitive testing demonstrates ongoing acquisition of developmental abilities, with cognitive, speech, and motor age equivalents measuring one to two standard deviations below the normative mean. His neurodevelopment is significantly above the natural history of untransplanted Hurler syndrome patients.
    explanation: >-
      This is the single reported patient behind the first-in-human
      intracisternal AAV9-IDUA claim in the description. It is an open-label,
      uncontrolled, single-patient experience in which the child also continued
      weekly intravenous enzyme infusions throughout, so it supports
      therapeutic potential for the CNS branch rather than establishing that
      gene transfer corrects CNS disease.
- name: Hematopoietic stem cell transplantation
  description: >-
    Early hematopoietic stem cell transplantation is the standard disease-modifying
    therapy for severe Hurler syndrome and offers the best chance to preserve
    neurocognitive function. It is disease-modifying rather than curative:
    long-term follow-up of successfully transplanted patients documents
    considerable residual disease burden with corrective surgical interventions
    at every decade, and restrictive lung disease in every treated MPS I
    patient able to complete pulmonary function testing.
  therapeutic_modality: CELL_THERAPY
  treatment_term:
    preferred_term: hematopoietic stem cell transplantation
    term:
      id: NCIT:C15431
      label: Hematopoietic Cell Transplantation
  target_mechanisms:
  - target: IDUA enzyme deficiency
    treatment_effect: RESTORES
    description: >-
      Donor-derived hematopoiesis can restore alpha-L-iduronidase enzyme levels;
      normal post-HCT enzyme levels predict better long-term organ outcomes.
    evidence:
    - reference: PMID:25624320
      reference_title: "Long-term outcome of Hurler syndrome patients after hematopoietic cell transplantation: an international multicenter study."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        A normal α-l-iduronidase enzyme level obtained post-HCT was another highly significant predictor for superior long-term outcome in most organ systems.
      explanation: >-
        This supports restored enzyme level as the proximal disease-modifying
        mechanism of HCT in Hurler syndrome.
  evidence:
  - reference: PMID:30442189
    reference_title: "Enzyme replacement therapy: efficacy and limitations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      For severe MPS I patients (Hurler), early haematopoietic stem cell transplantation is the gold standard
    explanation: >-
      This directly names early HSCT as the gold-standard treatment for severe
      Hurler syndrome.
  - reference: PMID:25624320
    reference_title: "Long-term outcome of Hurler syndrome patients after hematopoietic cell transplantation: an international multicenter study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Preservation of cognitive function at HCT and a younger age at transplantation were major predictors for superior cognitive development posttransplant.
    explanation: >-
      This large multicenter follow-up study supports early transplantation to
      preserve neurodevelopmental outcome.
  - reference: PMID:32713717
    reference_title: "The evolution of pulmonary function in childhood onset Mucopolysaccharidosis type I."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All patients had restrictive lung disease. Cobb angle and male sex were significantly associated with more severe outcomes in the HSCT cohort, with 49% having severe to very severe disease.
    explanation: >-
      Restrictive lung disease was present in every treated MPS I patient able
      to perform testing, and was severe or very severe in about half of the
      transplanted cohort. This supports the description's statement that
      transplantation modifies rather than eliminates the somatic disease.
- name: Enzyme replacement therapy
  description: >-
    Intravenous laronidase improves somatic storage manifestations in Hurler
    syndrome but does not adequately treat central nervous system disease.
  treatment_term:
    preferred_term: enzyme replacement therapy
    term:
      id: NCIT:C16221
      label: Protein Replacement Therapy
  target_mechanisms:
  - target: Dermatan sulfate and heparan sulfate accumulation
    treatment_effect: INHIBITS
    description: >-
      Enzyme replacement reduces systemic glycosaminoglycan storage biomarkers
      and liver/spleen volume, while having limited penetration into cartilage,
      bone, eyes, and the CNS.
    evidence:
    - reference: PMID:30442189
      reference_title: "Enzyme replacement therapy: efficacy and limitations."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        While ERT is effective in reducing urinary glycosaminoglycans (GAGs) and liver and spleen volume, cartilaginous organs such as the trachea and bronchi, bones and eyes are poorly impacted by ERT probably due to limited penetration in the specific tissue.
      explanation: >-
        Reduced urinary GAGs support inhibition of the glycosaminoglycan storage
        branch, with tissue-penetration limits noted by the review.
    - reference: PMID:41163043
      reference_title: "Safety and efficacy of laronidase in Chinese patients with mucopolysaccharidosis type I: a phase IV, single-arm, open-label, multicenter study."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Laronidase consistently reduced uGAGs levels from baseline to week 26, with a percentage change of -64.61%
      explanation: >-
        A phase IV trial quantifies the size of the substrate-storage reduction
        achieved by laronidase, giving the INHIBITS link a magnitude rather than
        a direction alone. The trial is single-arm and open-label in 12
        patients, and urinary GAG is a systemic surrogate that does not report
        cartilage, bone, eye, or CNS storage.
  evidence:
  - reference: PMID:30442189
    reference_title: "Enzyme replacement therapy: efficacy and limitations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Enzyme replacement therapy (ERT) is available for mucopolysaccharidosis (MPS) I, MPS II, MPS VI, and MPS IVA.
    explanation: >-
      This directly confirms availability of enzyme replacement therapy for MPS I,
      including Hurler syndrome.
  - reference: PMID:30442189
    reference_title: "Enzyme replacement therapy: efficacy and limitations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      ERT in the present formulations also does not cross the blood-brain barrier, with the consequence that the central nervous system is not cured by ERT.
    explanation: >-
      This explains the key limitation of ERT in severe Hurler syndrome, where
      CNS disease is clinically important.
differential_diagnoses:
- name: Hurler-Scheie syndrome
  description: >-
    Hurler-Scheie syndrome is an attenuated MPS I phenotype that overlaps with
    Hurler syndrome through IDUA deficiency and glycosaminoglycan storage but
    usually has less severe neurologic involvement and slower progression.
  distinguishing_features:
  - Minimal or delayed central nervous system involvement favors Hurler-Scheie syndrome.
  - Very early infancy-onset multisystem disease with severe neurodevelopmental risk favors Hurler syndrome.
  disease_term:
    preferred_term: Hurler-Scheie syndrome
    term:
      id: MONDO:0011759
      label: Hurler-Scheie syndrome
  evidence:
  - reference: PMID:28193245
    reference_title: "Early disease progression of Hurler syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      However, diagnostic tests for MPS I are of limited value in predicting whether a child will develop severe central nervous system disease associated with Hurler syndrome, or minimal or no central nervous system involvement associated with the attenuated phenotypes (Hurler-Scheie and Scheie syndromes).
    explanation: >-
      This explicitly distinguishes severe Hurler syndrome from the attenuated
      Hurler-Scheie phenotype based on CNS involvement.
- name: Scheie syndrome
  description: >-
    Scheie syndrome is the mildest MPS I phenotype and should be distinguished
    from Hurler syndrome by its attenuated course and relative absence of early
    severe neurodevelopmental disease.
  distinguishing_features:
  - Attenuated somatic disease with minimal or no CNS involvement favors Scheie syndrome.
  - Infantile onset with rapid multisystem progression favors Hurler syndrome.
  disease_term:
    preferred_term: Scheie syndrome
    term:
      id: MONDO:0011760
      label: Scheie syndrome
  evidence:
  - reference: PMID:28193245
    reference_title: "Early disease progression of Hurler syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      However, diagnostic tests for MPS I are of limited value in predicting whether a child will develop severe central nervous system disease associated with Hurler syndrome, or minimal or no central nervous system involvement associated with the attenuated phenotypes (Hurler-Scheie and Scheie syndromes).
    explanation: >-
      This abstract directly identifies Scheie syndrome as an attenuated MPS I
      phenotype that must be distinguished from Hurler syndrome.
clinical_trials: []
datasets: []
notes: >-
  Asta deep research was run as requested and identified one useful Hurler
  natural-history paper, but primary curation relied mainly on directly reviewed
  PubMed sources and existing cached references because much of the retrieval
  output was not disease-specific.
discussions:
- discussion_id: mismatch_hurler_immune_requirement_for_aortic_disease
  prompt: >-
    Does the immune activation that is required for aortic dilation in
    immunocompetent MPS I mice also mediate aortic and valvular disease in
    human Hurler syndrome?
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#Progressive skeletal and multisystem organ injury
  - phenotypes#Abnormal heart valve morphology
  rationale: >-
    Immunocompetent C57BL/6 MPS I mice develop ascending aortic dilation,
    aortic insufficiency and reduced left ventricular function, while
    immunodeficient NSG MPS I mice with the same degree of urinary
    glycosaminoglycan elevation do not. The immunocompetent aortas upregulated
    all eleven components of the inflammasome pathway and carried medial
    macrophage and adventitial T-cell infiltrates that the immunodeficient
    aortas lacked. If that dependency holds in people, glycosaminoglycan
    storage is not by itself sufficient for the cardiac phenotype, and
    anti-inflammatory adjunctive therapy becomes a plausible addition to
    enzyme restoration. Three things keep this out of the causal graph. The
    study is small, with 12 immunocompetent and 8 immunodeficient mutant male
    mice, and its authors describe it as a preliminary study. Tissue
    glycosaminoglycan was never quantified, only urinary excretion, so
    equivalent storage in the aortic wall is assumed rather than shown. The two
    strains differ in genetic background as well as in immune competence. No
    human study has tested immune suppression or inflammasome blockade for MPS
    I cardiovascular disease.
  proposed_experiments:
  - experiment_id: mps1_valve_inflammasome_immunoprofiling
    name: Immune profiling of explanted MPS I cardiac valve and aortic tissue
    description: >-
      Immunohistochemical and transcriptional profiling of valve and aortic
      tissue removed at surgery from MPS I patients against age-matched
      non-MPS surgical controls, scoring macrophage and T-cell infiltration and
      inflammasome component expression alongside a quantitative measure of
      tissue glycosaminoglycan storage rather than staining intensity alone.
    would_support:
    - pathophysiology#Progressive skeletal and multisystem organ injury
    - phenotypes#Abnormal heart valve morphology
    supporting_outcome:
    - >-
      Macrophage and T-cell infiltration with inflammasome component
      upregulation in MPS I valve and aortic tissue, scaling with lesion
      severity rather than with storage burden alone.
    refuting_outcome:
    - >-
      Storage-laden MPS I valve tissue showing no more immune infiltration or
      inflammasome expression than controls, which would confine the mouse
      finding to the model.
  evidence:
  - reference: PMID:35165009
    reference_title: "Contribution of the innate and adaptive immune systems to aortic dilation in murine mucopolysaccharidosis type I."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Ascending aortic diameters were significantly greater, left ventricular function significantly decreased, and AI significantly more frequent in B6 MPSI mice compared to NSG MPSI mice (p < 0.0001, p = 0.008 and p = 0.02, respectively); NSG and B6 WT mice showed no changes.
    explanation: >-
      The cardiac phenotype separates immunocompetent from immunodeficient MPS
      I mice, which is the observation that makes translation to human disease
      the open question recorded here.
  - reference: PMID:35165009
    reference_title: "Contribution of the innate and adaptive immune systems to aortic dilation in murine mucopolysaccharidosis type I."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      These results suggest that the innate and adaptive immune systems play a role in these cardiac findings which may be relevant to human MPSI.
    explanation: >-
      The authors state human relevance as a suggestion rather than a
      demonstrated result, which is precisely the mismatch this discussion
      records.
- discussion_id: gap_hurler_residual_disease_after_enzyme_restoration
  prompt: >-
    Why does considerable residual disease burden persist in every successfully
    transplanted Hurler patient, and does it reflect secondary cascades that
    have become independent of ongoing glycosaminoglycan storage?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - treatments#Hematopoietic stem cell transplantation
  - pathophysiology#Dermatan sulfate and heparan sulfate accumulation
  rationale: >-
    Transplantation restores donor-derived alpha-L-iduronidase, and a normal
    post-transplant enzyme level predicts superior long-term outcomes across
    organ systems. Yet residual burden requiring corrective surgery is observed
    in all patients at every decade of follow-up, and restrictive lung disease
    is present in every treated patient able to complete testing. Two
    explanations fit these data and have not been separated. Damage may accrue
    irreversibly before transplantation, which is typically performed near two
    years of age, and circulating enzyme may reach avascular cartilage, bone,
    heart valve and cornea poorly, which is what the enzyme replacement
    literature already reports. Alternatively, secondary cascades downstream of
    storage may become self-sustaining and stop responding to substrate
    clearance. Which is right determines whether the remedy is earlier or
    better enzyme delivery, or a second agent aimed at a downstream cascade.
    Serial multi-omic sampling from before transplantation through several
    years afterwards, and conditional restoration of Idua at different disease
    stages in animals, would separate them.
  evidence:
  - reference: PMID:33517895
    reference_title: "Long term disease burden post-transplantation: three decades of observations in 25 Hurler patients successfully treated with hematopoietic stem cell transplantation (HSCT)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Despite HSCT, considerable residual disease burden and ensuing corrective surgical interventions were observed in all, and at every decade of follow-up post HSCT.
    explanation: >-
      Three decades of follow-up in 25 successfully transplanted Hurler
      patients establish the observation this gap is about: enzyme restoration
      that is sufficient to change the natural history does not stop somatic
      disease accruing.
references:
- reference: PMID:20301341
  title: Mucopolysaccharidosis Type I.
  tags:
  - GeneReviews

📚

References & Deep Research

References

1

PMID:20301341

Mucopolysaccharidosis Type I.

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)

Record notes

Asta deep research was run as requested and identified one useful Hurler natural-history paper, but primary curation relied mainly on directly reviewed PubMed sources and existing cached references because much of the retrieval output was not disease-specific.

Asta ▸

Asta Literature Retrieval: Pathophysiology and clinical mechanisms of Hurler syndrome. Core disease mechanisms, molecular and cellular pathways,...

Asta Scientific Corpus Retrieval 20 citations 2026-04-11T12:36:57.499997

Asta Literature Retrieval: Pathophysiology and clinical mechanisms of Hurler syndrome. Core disease mechanisms, molecular and cellular pathways,...

This report is retrieval-only and is generated directly from Asta results.

Papers retrieved: 20
Snippets retrieved: 20

Relevant Papers

[1] Targeting Hepatic Stellate Cells for the Prevention and Treatment of Liver Cirrhosis and Hepatocellular Carcinoma: Strategies and Clinical Translation

Authors: Hao Xiong, Jinsheng Guo
Year: 2025
Venue: Pharmaceuticals
URL: https://www.semanticscholar.org/paper/76e92127053136900f7e3f10e2c9278251ced5d2
DOI: 10.3390/ph18040507
PMID: 40283943
PMCID: 12030350
Citations: 8
Summary: HSC-targeted approaches using specific surface markers and receptors may enable the selective delivery of drugs, oligonucleotides, and therapeutic peptides that exert optimized anti-fibrotic and anti-HCC effects.
Evidence snippets:
Snippet 1 (score: 0.400) > Significant progress has been made in elucidating the cellular and molecular mechanisms of liver fibrosis; however, only a few findings have been successfully translated into clinical applications. Firstly, the high cost of drug development and target validation necessitates prolonged timelines and substantial financial investment. Secondly, as regulatory requirements become more stringent, there is an increasing demand for drugs with well-defined clinical efficacy and safety profiles. Moreover, the efficacy observed in animal models often fails to fully translate to clinical settings due to differences in pharmacokinetics, extracellular matrix (ECM) cross-linking, and disease pathophysiology. Despite advancements in anti-fibrotic drug development, accurately identifying ideal noninvasive biomarkers for fibrotic activity and establishing consensus on optimal clinical endpoints remain significant challenges [113,114]. > Currently, addressing the underlying cause remains the only proven strategy to halt or reverse liver fibrosis progression, while the development of effective anti-fibrotic therapies continues to pose a major challenge in liver disease management. Over the past few decades, substantial progress has been made in elucidating the cellular and molecular mechanisms underlying liver fibrosis. Liver fibrosis is a complex pathological change involving multiple cells, factors, and pathways, and the study of the cellular and molecular mechanisms of its occurrence and development provides an important theoretical basis and therapeutic target for clinical drug development. It is anticipated that improved animal models and well-designed clinical trials will facilitate the successful translation of anti-fibrotic research into effective clinical treatments in the near future.

[2] Early disease progression of Hurler syndrome

Authors: B. Kiely, J. L. Kohler, H. Coletti, M. Poe, M. Escolar
Year: 2017
Venue: Orphanet Journal of Rare Diseases
URL: https://www.semanticscholar.org/paper/a895995e4e765d9edf8bb31d016a93075f63c958
DOI: 10.1186/s13023-017-0583-7
PMID: 28193245
PMCID: 5307824
Citations: 73
Influential citations: 4
Summary: The aim of this study was to characterize the progression and timing of symptom onset in infants with Hurler syndrome and to determine the extent to which early clinical manifestations of MPS I can predict phenotype and treatment outcomes.
Evidence snippets:
Snippet 1 (score: 0.390) > BackgroundNewborn screening for mucopolysaccharidosis type I (MPS I) shows promise to improve outcomes by facilitating early diagnosis and treatment. However, diagnostic tests for MPS I are of limited value in predicting whether a child will develop severe central nervous system disease associated with Hurler syndrome, or minimal or no central nervous system involvement associated with the attenuated phenotypes (Hurler–Scheie and Scheie syndromes). Given that the optimal treatment differs between Hurler syndrome and the attenuated MPS I phenotypes, the absence of a reliable prognostic biomarker complicates clinical decision making for infants diagnosed through newborn screening. Information about the natural history of Hurler syndrome may aid in the management of affected infants, contribute to treatment decisions, and facilitate evaluation of treatment effectiveness and prognosis. Thus, the aim of this study was to characterize the progression and timing of symptom onset in infants with Hurler syndrome.ResultsClinical data from 55 patients evaluated at a single center were retrospectively reviewed. Information about each child’s medical history was obtained following a standardized protocol including a thorough parent interview and the review of previous medical records. All patients underwent systematic physical and neurodevelopmental evaluations by a multidisciplinary team. Nearly all patients (98%) showed signs of disease during the first 6 months of life. Common early disease manifestations included failed newborn hearing screen, respiratory symptoms, difficulty latching, and otitis media. Other symptoms such as kyphosis, corneal clouding, cardiac disease, joint restrictions, and enlarged head circumference typically appeared slightly later (median age, 8–10 months). During the first 12 months, gross motor development was the most severely affected area of functioning, and a significant number of patients also experienced language delays. Cognition was typically preserved during this period.ConclusionsIn this large cohort of patients with Hurler syndrome, the vast majority showed signs and symptoms of disease during the first months of life. More research is needed to determine the extent to which early clinical manifestations of MPS I can predict phenotype and treatment outcomes.

[3] Novel Approaches to Studying SLC13A5 Disease

Authors: Adriana S. Beltran
Year: 2024
Venue: Metabolites
URL: https://www.semanticscholar.org/paper/8469c534cd81d96f84b61e2d963dead12088feb7
DOI: 10.3390/metabo14020084
PMID: 38392976
PMCID: 10890222
Citations: 2
Summary: Current technologies for generating patient-specific induced pluripotent stem cells (iPSCs) and their inherent advantages and limitations are discussed, followed by a summary of the methods for differentiating iPSCs into neurons, hepatocytes, and organoids.
Evidence snippets:
Snippet 1 (score: 0.388) > The precise pathophysiology underlying how SLC13A5 loss-of-function results in epilepsy refractory to treatment is a subject of open and ongoing research. Several hypotheses suggest SLC13A5 alters metabolic pathways, leading to neuronal dysfunction. Conversely, therapeutic inhibition of NaCT in the liver is a target to improve metabolic diseases, including non-alcoholic fatty liver disease, obesity, and insulin resistance. Thus, functionally accurate modeling and characterization of the mechanisms involved in citrate transport disruption are critical for understanding its role in human disease. > IPSC-derived cellular systems are a powerful tool for modeling rare human genetic diseases, such as SLC13A5 (Figure 5). IPSCs derived from patients containing the genetic information of the disease can overcome the limitations of animal models, providing access to relevant human cell types that recapitulate the disease phenotype. For instance, patient-derived iPSCs differentiated into neurons or hepatocytes can be used to investigate molecular and cellular mechanisms, including citrate transport and accumulation, energy metabolism, oxidative stress, and other cellular processes. They can also be used to define the spectrum of the disease and how different mutations might lead to various disease severities, screen for potential therapeutic compounds that can restore the transporter function or ameliorate the symptoms, and enable personalized medicine approaches that can tailor treatments to individual patients based on their genetic background and disease severity. > transport disruption are critical for understanding its role in human disease. > IPSC-derived cellular systems are a powerful tool for modeling rare human genetic diseases, such as SLC13A5 (Figure 5). IPSCs derived from patients containing the genetic information of the disease can overcome the limitations of animal models, providing access to relevant human cell types that recapitulate the disease phenotype. For instance, patient-derived iPSCs differentiated into neurons or hepatocytes can be used to investigate molecular and cellular mechanisms, including citrate transport and accumulation, energy metabolism, oxidative stress, and other cellular processes.

[4] Musculoskeletal manifestations in mucopolysaccharidosis type I (Hurler syndrome) following hematopoietic stem cell transplantation

Authors: M. Schmidt, S. Breyer, U. Löbel, S. Yarar, R. Stücker et al.
Year: 2016
Venue: Orphanet Journal of Rare Diseases
URL: https://www.semanticscholar.org/paper/0b2cdfb987e8047fca22d990fa1a1d468a32028c
DOI: 10.1186/s13023-016-0470-7
PMID: 27392569
PMCID: 4938899
Citations: 55
Influential citations: 2
Summary: Joint mobility, odontoid hypoplasia and craniocervical stenosis might stabilize or even improve in Hurler patients following HSCT, however, skeletal complications are frequently observed and the overall burden of orthopedic disease is significant.
Evidence snippets:
Snippet 1 (score: 0.385) > Mucopolysaccharidosis (MPS) type I is an autosomal recessive inherited metabolic disorder caused by a deficiency of lysosomal α-iduronidase (IDUA, EC 3.2.1.76). Consequently, the glycosaminoglycans (GAGs) heparanand dermatan-sulfate accumulate within the lysosomes causing cellular dysfunction [1,2]. The incidence of MPS I in Germany has been estimated as 0.69 cases per 100,000 births [3]. Clinical severity and progression of the disease vary significantly in affected patients. Based on the clinical appearance three different subtypes of MPS I are classified: the classical severe phenotype referred to as Hurler syndrome (MPS I-H), the less severe Hurler-Scheie syndrome (MPS I-H/S) and the attenuated form -Scheie syndrome (MPS I-S) [1,2,4]. Clinical symptoms of Hurler syndrome include the characteristically coarse facial features, corneal clouding, hearing impairment, cardiac involvement, obstructive and restrictive pulmonary disease and hepatosplenomegaly. With increasing age patients also show progressive neurological decline. Musculoskeletal involvement is common in all subtypes of MPS I. Skeletal abnormalities include: a short stature, degenerative joint disease and a skeletal dysplasia referred to as dysostosis multiplex [5,6]. > The pathophysiology of the bone disease is still not well understood. Disordered growth plate chondrocyte organization and trabecular architecture were observed in several animal models of different MPS subtypes [7]. As shown in studies in MPS I mice, accumulation of GAGs could lead to inactivation of the major osteoclastic protease cathepsin K, which in turn may result in reduction in cartilage degradation and contribute to the bone pathology observed in MPS [8]. The progressive arthropathy is assumed to be mediated by GAG accumulation, resulting in increased cytokine and chemokine recruitment (e.g.

[5] Modeling psychiatric disorders: from genomic findings to cellular phenotypes

Authors: Anna Falk, Vivi M. Heine, A. Harwood, Patrick F. Sullivan, M. Peitz et al.
Year: 2016
Venue: Molecular Psychiatry
URL: https://www.semanticscholar.org/paper/235b41240d78140de7ab06a3ad8a7d0b1bdff1a5
DOI: 10.1038/mp.2016.89
PMID: 27240529
PMCID: 4995546
Citations: 77
Influential citations: 2
Summary: The challenges for modeling of psychiatric disorders, potential solutions and how iPSC technology can be used to develop an analytical framework for the evaluation and therapeutic manipulation of fundamental disease processes are critically reviewed.
Evidence snippets:
Snippet 1 (score: 0.382) > The key challenge for iPSC-based disease modeling is to identify one or more relevant cellular phenotypes that accurately represent the disease pathophysiology. Increasing numbers of reports have demonstrated that for many diseases specific pathophysiology can be captured in human iPSC-based disease models. These range from cardiovascular disease, 44,45 cancer, 46,47 ocular disease, 48,49 diabetes mellitus 50,51 and neurological disorders of the brain. 52,53 Can the same approach be applied to complex psychiatric disorders? > The problem is that almost all psychiatric disorders are characterized by clinical signs and symptoms, but lack independent verification from objective biomarkers. Thus, how might these clinical phenotypes manifest themselves in terms of cell behavior? The identity of robust cellular 'readouts', which typify any psychiatric disorder, is a crucial unsolved problem and an area of intense study 54 (Table 2). When satisfactorily answered, this will herald a new degree of biological objectivity and quantification for the study of psychiatric disorders. > The aim is to find a single or small number of cell phenotypes or parameters that strongly associate with psychiatric disorders, and establish a cellular profile characteristic of cells derived from the general patient population. Although a consensus set of cellular phenotypes for psychiatric disorder is yet to be established, we can define some of their desired characteristics. First, cellular phenotypes have to relate to the biological pathways identified by genetics. Second, although there are many risk genes in disparate biological pathways, at some level, phenotypes should converge onto a much smaller grouping. Third, phenotypes need to be quantifiable. Finally, to be useful for drug development cellular phenotypes should be reversed by pharmacological treatment, although not necessarily by drugs in current use. > Although human iPSC-based approaches underrepresent the complexity of the human central nervous system, cellular phenotypes are likely to lie more proximal to molecular disease mechanisms than phenotypes seen at the level of a tissue or organism, 55 and thus may bypass compensatory homeostatic (2) Gene expression profiles of SCZ human iPSC neurons identified altered expression of many components of the cyclic AMP and WNT signaling pathways. > (3

[6] New therapeutic targets in rare genetic skeletal diseases

Authors: M. Briggs, Peter A. Bell, M. Wright, K. A. Pirog
Year: 2015
Venue: Expert Opinion on Orphan Drugs
URL: https://www.semanticscholar.org/paper/1363107f71ae6d2d60abca471cddf3da5d13644b
DOI: 10.1517/21678707.2015.1083853
PMID: 26635999
PMCID: 4643203
Citations: 37
Influential citations: 1
Summary: An overview of disease mechanisms that are shared amongst groups of different GSDs and potential therapeutic approaches that are under investigation are described to generate critical mass for the identification and validation of novel therapeutic targets and biomarkers.
Evidence snippets:
Snippet 1 (score: 0.381) > proteins of the cartilage ECM such as type II collagen [50]. However, emerging knowledge suggests that the primary genetic defect may be less important than the cells' response to the expression of the mutant gene product [107]. Moreover, the largely overlooked response of a cell (i.e. chondrocyte) to the abnormal extracellular environment is also important for disease progression as illustrated by several GSDs discussed in this review. > It is important that 'omics'-based approaches and technologies are systematically applied to the study of rare GSDs so that definitive reference profiles and disease signatures are generated for each phenotype. These can then be used in a Systems Biology approach to identify both common and dissimilar pathological signatures and disease mechanisms. This approach is entirely dependent upon relevant in vitro and in vivo models (and also novel 'disease-mechanism phenocopies' [107]) for testing new diagnostic and prognostic tools and for determining the molecular mechanisms that underpin the pathophysiology so that effective therapeutic treatments can be developed and validated. This approach will eventually lead to personalized treatments and care strategies centred on shared disease mechanisms with the use of relevant biomarkers to monitor the efficacy of treatment and disease progression. > It is vital that all relevant stakeholders are involved from the outset in defining the appropriate outcomes of any potential therapeutic regime. The perceptions of a successful therapy can differ widely between the clinical academic community and the relevant patient-support groups and it is vital that there is engagement on all these issues. > In summary, the identification of causative genes and mutations for GSDs over the last 20 years, coupled with the generation and in-depth analysis of a plethora of relevant cell and mouse models, has derived new knowledge on disease mechanisms and suggested potential therapeutic targets. The fast-evolving hypothesis that clinically disparate diseases can share common disease mechanisms is a powerful concept that will generate critical mass for the identification and validation of novel therapeutic targets and biomarkers.

[7] Therapies for Mitochondrial Disease: Past, Present, and Future

Authors: Megan Ball, Nicole J. Van Bergen, A. Compton, David R Thorburn, S. Rahman et al.
Year: 2025
Venue: Journal of Inherited Metabolic Disease
URL: https://www.semanticscholar.org/paper/196ee50a950f29bc4134cfb8fe6bdfa9a3a1468b
DOI: 10.1002/jimd.70065
PMID: 40714961
PMCID: 12301291
Citations: 2
Summary: The latest developments in the pursuit to identify effective treatments for mitochondrial disease are examined and the barriers impeding their success in translation to clinical practice are discussed.
Evidence snippets:
Snippet 1 (score: 0.379) > Mitochondrial disease is a diverse group of clinically and genetically complex disorders caused by pathogenic variants in nuclear or mitochondrial DNA‐encoded genes that disrupt mitochondrial energy production or other important mitochondrial pathways. Mitochondrial disease can present with a wide spectrum of clinical features and can often be difficult to recognize. These conditions can be devastating; however, for the majority, there is no targeted treatment. In the last 60 years, mitochondrial medicine has experienced significant evolution, moving from the pre‐molecular era to the Age of Genomics in which considerable gene discovery and advancement in our understanding of the pathophysiology of mitochondrial disease have been made. In the last decade, in response to the urgent need for effective treatments, a wide range of emerging therapies have been developed, driven by innovative approaches addressing both the genetic and cellular mechanisms underpinning the diseases. Emerging therapies include dietary intervention, small molecule therapies aimed to restore mitochondrial function, stem cell or liver transplantation, and gene or RNA‐based therapies. However, despite these advances, translation to clinical practice is complicated by the sheer genetic and clinical complexity of mitochondrial disease, difficulty in efficient and precise delivery of therapies to affected tissues, rarity of individual genetic conditions, lack of reliable biomarkers and clinically relevant outcome measures, and the dearth of natural history data. This review examines the latest developments in the pursuit to identify effective treatments for mitochondrial disease and discusses the barriers impeding their success in translation to clinical practice. While treatment for mitochondrial disease may be on the horizon, many challenges must be addressed before it can become a reality.

[8] Building a knowledge graph to enable precision medicine

Authors: P. Chandak, Kexin Huang, M. Zitnik
Year: 2022
Venue: Scientific Data
URL: https://www.semanticscholar.org/paper/5cc58bcfb9bf39d4114eab88fca36eb0ce36afd9
DOI: 10.1038/s41597-023-01960-3
PMID: 36732524
PMCID: 9893183
Citations: 476
Influential citations: 36
Summary: PrimeKG is presented, a multimodal knowledge graph for precision medicine analyses that contains an abundance of ‘indications’, ‘contradictions’, and ‘off-label use’ drug-disease edges that lack in other knowledge graphs and can support AI analyses of how drugs affect disease-associated networks.
Evidence snippets:
Snippet 1 (score: 0.379) > gene/protein class. (c) Illustrated is the process of harmonizing these primary data records to extract relationships between node types. (d) The left side illustrates PrimeKG, and the right side shows all the textual sources of clinical information on drugs and diseases. The node type legend is consistent across the figure. Abbreviations -MF: molecular function, BP: biological process, CC: cellular component, PPI: protein-protein interactions, DO: disease ontology, MONDO: MONDO disease ontology, Entrez: Entrez gene, GO: gene ontology, UMLS: unified medical language system, HPO: human phenotype ontology, CTD: comparative toxicogenomics database, SIDER: side effect resource. > www.nature.com/scientificdata www.nature.com/scientificdata/ International Classification of Diseases (ICD), and Medical Dictionary for Regulatory Activities (MedDRA), it was our preferred ontology for defining diseases. We retrieved the ontology from http://purl.obolibrary.org/ obo/MONDO.obo on 31 May 2021. Processing involved parsing the ontology file to extract disease terms in the ontology, parent-child relationships, subsets of diseases, cross references to other ontologies, and definitions of disease terms. The processed data contains 64,388 disease-disease edges. > Orphanet. Orphanet 48 is a database that focuses on gathering knowledge about rare diseases. The Orphanet resource at https://www.orpha.net/consor/cgi-bin/Disease_Search_List.php?lng=EN has curated information about definitions, prevalence, management and treatment, epidemiology, and clinical description for 9,348 rare diseases. We retrieved the resource data and extracted disease features on 10 May 2021 using the orpha.py script available in the PrimeKG repository. > Let us illustrate features in PrimeKG for rare Hurler syndrome with the Orphanet ID 93473. Hurler syndrome is the most severe form of mucopolysaccharidosis type 1, a rare lysosomal storage disease characterized by skeletal abnormalities, cognitive impairment, heart disease, Four sources of physical protein-protein interactions. Protein-protein interactions (PP

[9] Human Dermal Fibroblast: A Promising Cellular Model to Study Biological Mechanisms of Major Depression and Antidepressant Drug Response

Authors: P. Mesdom, R. Colle, É. Lebigot, S. Trabado, Eric Deflesselle et al.
Year: 2020
Venue: Current Neuropharmacology
URL: https://www.semanticscholar.org/paper/79368e365458486de96794333613c12a6063bf54
DOI: 10.2174/1570159X17666191021141057
PMID: 31631822
PMCID: 7327943
Citations: 12
Summary: This review highlights the great and still underused potential of HDF, which stands out as a very promising tool in the understanding of MDD and AD mechanisms of action.
Evidence snippets:
Snippet 1 (score: 0.366) > Background: Human dermal fibroblasts (HDF) can be used as a cellular model relatively easily and without genetic engineering. Therefore, HDF represent an interesting tool to study several human diseases including psychiatric disorders. Despite major depressive disorder (MDD) being the second cause of disability in the world, the efficacy of antidepressant drug (AD) treatment is not sufficient and the underlying mechanisms of MDD and the mechanisms of action of AD are poorly understood. Objective The aim of this review is to highlight the potential of HDF in the study of cellular mechanisms involved in MDD pathophysiology and in the action of AD response. Methods The first part is a systematic review following PRISMA guidelines on the use of HDF in MDD research. The second part reports the mechanisms and molecules both present in HDF and relevant regarding MDD pathophysiology and AD mechanisms of action. Results HDFs from MDD patients have been investigated in a relatively small number of works and most of them focused on the adrenergic pathway and metabolism-related gene expression as compared to HDF from healthy controls. The second part listed an important number of papers demonstrating the presence of many molecular processes in HDF, involved in MDD and AD mechanisms of action. Conclusion The imbalance in the number of papers between the two parts highlights the great and still underused potential of HDF, which stands out as a very promising tool in our understanding of MDD and AD mechanisms of action

[10] Effects of SARS-CoV-2 Spike S1 Subunit on the Interplay Between Hepatitis B and Hepatocellular Carcinoma Related Molecular Processes in Human Liver

Authors: Giovanni Colonna
Year: 2024
Venue: Livers
URL: https://www.semanticscholar.org/paper/2f31a9d4b1e7e8e8c18f5b714e724960c624f61d
DOI: 10.3390/livers5010001
Summary: The interactome tells us that genes involved in HCC and HVB-related pathways have the potential to activate disease processes and can be considered as a gold standard for personalized molecular medicine diagnoses.
Evidence snippets:
Snippet 1 (score: 0.365) > The interactions we studied derive from controlled in vivo studies in different cellular models without direct links to specific clinical phenotypes. Model cell systems mimic an organism but are not the organism [93][94][95][96]. This reinforces the idea that molecular interactions potentially reflect mechanistic processes rather than direct clinical outcomes. The multi-to-one or multi-multi correlations between molecular mechanisms and phenotypic expressions further complicate the assumption that molecular evidence can directly explain macroscopic disease processes like the progression from hepatitis to HCC. > In short, the SARS-CoV-2 S1 protein may induce microscopic conditions that develop differently based on individual phenotypic states, which is in line with the complexity of viral pathogenesis. This reflects the non-deterministic nature of interactome data-capturing potentialities rather than predicting phenotypic outcomes. We propose an approach to interpreting molecular data that avoids overgeneralization in linking it to clinical disease progression. We could use our molecular results as a gold standard against molecular data from specific patients to identify whether the metabolic system of the infected patient is implementing the mechanisms driving the progression of HBV infection. These processes should not be present in a healthy person. However, they could also be a clinically useful signal of the level of severity reached by the viral infection in a patient with previous morbidity. > We can now discuss in more detail some aspects of our results through our interpretation of the interactomics approach used by exploring the different levels at which molecular variability could influence the results. > 1. Phenotypic Heterogeneity in Liver Cells. Even without pre-existing liver diseases, subtle variations in liver cell signaling pathways or receptor expression could lead to diverse responses to the S1 protein. For instance, different tissues and even liver cell types variably express ACE2, a key receptor involved in SARS-CoV-2 entry [97]. If liver cells from two individuals express ACE2 at differing levels, the downstream signaling pathways activated by S1 binding will differ, leading to heterogeneity in the subsequent cellular response (e.g., stress, apoptosis, or immune modulation); > 2. S1's Influence on Liver-Specific Signaling Pathways. The S1 protein might activate or inhibit liver-specific pathways [98].

[11] 18O-assisted dynamic metabolomics for individualized diagnostics and treatment of human diseases

Authors: E. Nemutlu, Song Zhang, N. Juranic, A. Terzic, S. Macura et al.
Year: 2012
Venue: Croatian Medical Journal
URL: https://www.semanticscholar.org/paper/880f053c7f060db4b990e447d0a22c4b69372ddb
DOI: 10.3325/cmj.2012.53.529
PMID: 23275318
PMCID: 3541579
Citations: 28
Summary: The potential use of dynamic phosphometabolomic platform for disease diagnostics currently under development at Mayo Clinic is described and discussed briefly.
Evidence snippets:
Snippet 1 (score: 0.361) > Living cells represent an integrated and interacting network of genes, transcripts, proteins, small signaling molecules, and metabolites that define cellular phenotype and function. Traditionally the focus of biomedical research was on individual genes, single protein targets, single metabolites, and metabolic or signaling pathways. This "molecular reductionist" paradigm was based on the assumption that identifying genetic variations and molecular components would lead to discovery of cures for human diseases. However, most of diseases are complex and multi-factorial and the disease phenotype is determined by the alterations of multiple genes, pathways, proteins and metabolites (at cellular, tissue, and organismal levels). Therefore, an integrated "omics" approach is more viable direction for uncovering alterations in metabolic networks, disease mechanisms, and mechanisms of drug effects. > Recent advent of large-scale metabolomics and fluxomic (metabolite dynamics and metabolic flux analysis) completed the "omics revolution" (Figure 1), where genomics, transcriptomics, proteomics, metabolomics, and fluxomics all together complement phenotype determination of living organism. Such integrated "omics" cascades provide a framework for advances in system and network biology, integrative physiology, and system medicine as well as system pharmacology and regenerative medicine. Noteworthy is the "reverse omic" approach or "metabolomicsinformed pharmacogenomics, " where discovery of specific metabolite changes have led to discovery of genetic alterations (2). Therefore, bringing new "omics" technologies to clinical practice will improve disease diagnostics and treatment by targeting drugs and procedures for each unique transcriptomic and metabolomic profiles.

[12] Femoral Structure and Biomechanical Characteristics in Sanfilippo Syndrome Type-B Mice

Authors: F. Ashby, Evelyn J. Castillo, Yan Ludwig, Natalia K Andraka, Cong Chen et al.
Year: 2023
Venue: International Journal of Molecular Sciences
URL: https://www.semanticscholar.org/paper/46054e66f1842cffe6d4cbc20c3a81c8abae7ad9
DOI: 10.3390/ijms241813988
PMID: 37762291
PMCID: 10530914
Citations: 2
Summary: Bone mineral content (BMC), volumetric bone mineral density (vBMD), and biomechanical properties in femurs MPS IIIB C57BL/6 mice compared to phenotypic control C 57BL/ 6 mice are determined to suggest some skeletal features of the MPS IIB mouse model may be used as biomarkers of peripheral disease correction for preclinical treatment of MPSIIIB.
Evidence snippets:
Snippet 1 (score: 0.361) > Mucopolysaccharidosis (MPS) is a cluster of lysosomal storage diseases that affect the breakdown of glycosaminoglycans (GAGs), leading to each MPS type's molecular and clinical sequelae [1]. MPS diseases are categorized as Type-I, Type-II, Type-III, Type-IV, Type-VI, and Type-VII based on which enzyme in the respective GAG pathway is affected [2]. Type-V (Scheie syndrome) was later found to be a milder form of Type-I (Hurler syndrome), which affects the IDUA gene pathway. MPS I is known as Hurler's syndrome, and MPS II, known as Hunter's syndrome, are characterized by the accumulation of dermatan sulfate and heparan sulfate [3]. MPS Type-III, also known as Sanfilippo syndrome, is characterized by an inability to breakdown heparan sulfate alone. MPS VII, also known as Morquio syndrome, is characterized by the accumulation of dermatan sulfate, heparan sulfate, and chondroitin sulfate. It is worth noting that MPS Type-I, II, III, and VII all have heparan sulfate as a common GAG accumulation [2]. > All MPS types are afflicted with skeletal malformations, yet much remains to be elucidated about the mechanism of this. Heparan sulfate and other GAGs have been shown to stimulate Toll-like Receptor 4 (TLR-4) in human dendritic cells [4,5], resulting in the production of many cellular cytokines, such as TNF-α, that mediate neuroinflammation and abnormal bone ossification due to enhanced chondrocyte turnover [6][7][8][9]. In MPS I, II, and VI, a high TNF-α was shown to be associated with increased disability and pain [10]. It is also speculated that vitamin D deficiency plays a key role in osteological manifestations of MPS [11].

[13] Progress in the Management of Patients with Cholestatic Liver Disease: Where Are We and Where Are We Going?

Authors: Xin Luo, Lungen Lu
Year: 2024
Venue: Journal of Clinical and Translational Hepatology
URL: https://www.semanticscholar.org/paper/42239f0ce6e3997132a7eeccd6a9e6ff07f3d099
DOI: 10.14218/JCTH.2023.00519
PMID: 38974958
PMCID: 11224908
Citations: 8
Influential citations: 1
Summary: The recommended guidelines for the management of cholestatic disease and the progress of new drug research and development are summarized to provide an important reference for the clinical practice of cholestatic liver disease.
Evidence snippets:
Snippet 1 (score: 0.360) > The main reason for this unmet clinical need is the unclear mechanisms exploration of etiology in PBC and PSC. > The pathophysiology of PBC is largely elucidated and recent studies have focused on the initiating factors of the disease.It is generally accepted that PBC is a disease driven by both genetic and environmental factors, and is closely related to autoimmune dysfunction.For reasons that have not yet been elucidated, mitochondria in biliary epithelial cells (BECs) are attacked, leading to BEC dysfunction, bile duct injury, and cholestasis.A characteristic biochemical change in PBC patients is antimitochondrial antibody BEC seropositivity.One of the urgent questions to be answered is that although mitochondria are present in all nucleated cells, why are mitochondria in BECs but not other cells attacked in PBC patients. 58,59Study of this immunological mechanism is important for the development of new drugs that can target PBC and represents a new direction.The immune system may play an important role in the development of new drugs for PBC.Protection of BEC function is thought to be important.Because increased BEC apoptosis leads to bile duct dysfunction, the inhibition of BEC apoptosis is of great significance. 60It is also important to note that PBC is more common in women than in men. 61Does this suggest that sex hormones may be involved in the progression of PBC? Targeting the role of sex hormones in the progression of PBC is also an important direction for subsequent drug research and development. > Recent studies of the etiology of PSC have focused on the correlation of PSC and IBD.There is a controversy about whether PSC and IBD are two independent diseases or the same disease manifests in different organs.A lot of clinical evidence shows that the two diseases are similar, but further investigation is needed to determine a causal relationship between the two diseases.Although there is a strong correlation between the two diseases, a number of clinical trials have confirmed that drugs suitable for IBD have very limited benefits for the treatment of PSC, which suggests that pathophysiology of PSC differs from that of IBD. 62,63

[14] Current and Emerging Approaches for Nonalcoholic Steatohepatitis Treatment.

Authors: Ming-Ming Chen, Jingjing Cai, Yao Yu, Zhi‐Gang She, Hongliang Li
Year: 2019
Venue: Gene expression
URL: https://www.semanticscholar.org/paper/1f2b67b026eac95fc03f45146f25d55d11d6ca91
DOI: 10.3727/105221619X15536120524171
PMID: 30940296
Citations: 22
Influential citations: 1
Summary: The potential strategies and challenges in therapeutic approaches to treating NASH are reviewed and some agents targeting various vital molecules and pathways, including those impacting metabolic perturbations, inflammatory cascades and oxidative stress, are in clinical trials.
Evidence snippets:
Snippet 1 (score: 0.357) > Drug development for NASH requires clear mechanisms, appropriate animal models, progressive clinical trials, convenient efficacy evaluation, and follow-up methods. Many challenges impeding the translation from bench to bedside remain in this drug discovery process. The pathogenesis of NASH has not been entirely elucidated and has been debated for a long time, which is one of the bottlenecks in drug development. The "multiple-parallel hit" hypothesis was recently proposed, providing a more adequate explanation of how fatty acids and their metabolites promote NASH through multiple sequential or parallel cytotoxic pathways 110 . The pathogenesis of human NASH involves varied molecular pathways and complex progression with a dynamic bidirectional nature, which is unlikely to be the same in all patients, raising concern about individual differences. > The perfect animal model that mimics the pathophysiology of NASH and displays the most clinical characteristics of human disease as closely as possible does not exist, further increasing the difficulty in identifying and validating potential drug targets for human NASH. Many species, including mice, rabbits, pigs, and monkeys, are used to develop models with a liver phenotype resembling human NASH, and each has its advantages and disadvantages 111 . Recently, monkeys have been recommended as models of NASH due to similarities in liver anatomy, physiology, metabolism, and genetics to humans 112,113 . Monkey breeding has specific disadvantages including sophisticated genetic methods, housing, cost, and logistics. Moreover, the ideal pharmacodynamics of drugs in animal models do not necessarily replicate in human NASH. > Because of the slow progression to clinically significant outcomes in NASH, drug development has been delayed, and the potential time to market for drugs has been extended. The use of optimal surrogate endpoints for clinical trials in NASH is imperative for evaluating pharmacologic agents 114 . For purposes of accelerated approval, the surrogate endpoints used by the FDA can be achieved in a reasonably short timeframe. Biomarkers of NASH are helpful for the diagnosis, monitoring, and prognosis of disease progression and evaluation of the effects of new regimens, which is urgent in the field of NASH. In addition, existing methods of pharmacodynamic evaluation and follow-up are still insufficient to assess NASH progression and regression for drug development.

[15] Changes in Serum Proteomic Profiles at Different Stages of Pregnancy Toxemia in Goats

Authors: M. Uzti̇mür, C. N. Ünal, Gurler Akpinar
Year: 2025
Venue: Journal of Veterinary Internal Medicine
URL: https://www.semanticscholar.org/paper/4b9c488b5dbd65d7b26fd2ad9aed70e8c4b59942
DOI: 10.1111/jvim.70139
PMID: 40492724
PMCID: 12150350
Summary: Understanding the serum proteome profiles of goats with pregnancy toxemia might help identify the proteomes and pathways responsible for the development of this disease and improve diagnosis and treatment.
Evidence snippets:
Snippet 1 (score: 0.356) > The pathophysiology and progression of this disease are not fully understood. > Traditional biomedical research has focused on the analysis of single genes, proteins, metabolites, or metabolic pathways in diseases. This molecular reductionist approach is based on the assumption that identifying genetic variations and molecular components will lead to new treatments for diseases [13][14][15][16]. However, many diseases are complex and multifactorial, and in order to determine the phenotype of such diseases, it is necessary to understand the changes that occur in more than one gene, pathway, protein, or metabolite at the cellular, tissue, and organismal levels [17][18][19]. Therefore, in recent years, proteomics, as one field of multi-omics technologies, has helped in evaluating the complex pathogenetic mechanisms of different diseases from a broad perspective and has made substantial contributions [20,21]. In veterinary medicine, proteomic analysis of metabolic diseases such as ketosis [16], hypocalcemia [22], and fatty liver [23] in dairy cows has contributed valuable insights for the definition of new pathophysiological pathways and new diagnosis and treatment protocols for these diseases. The proteomic approach can contribute importantly to a broad and detailed understanding of the changes that occur at the organismal level associated with the increase in BHBA concentration in goats with pregnancy toxemia. Our aim was to evaluate the serum protein profiles of goats with SPT or CPT using proteomic techniques to determine the proteomic profiles of these animals and to identify the relevant pathophysiological mechanisms.

[16] Exploring the molecular mechanisms of subarachnoid hemorrhage and potential therapeutic targets: insights from bioinformatics and drug prediction

Authors: Yi Liu, Yang Zhang, Huan Wei, Li Wang, Lishang Liao
Year: 2025
Venue: Scientific Reports
URL: https://www.semanticscholar.org/paper/19a91d9c8cabec6a5a186729d545077e252ecb67
DOI: 10.1038/s41598-025-97642-8
PMID: 40229542
PMCID: 11997208
Summary: The findings not only elucidate the molecular mechanisms underlying SAH but also provide robust bioinformatics and experimental evidence supporting IRN as a promising therapeutic candidate, offering novel insights for future intervention strategies in SAH.
Evidence snippets:
Snippet 1 (score: 0.352) > involved in SAH pathology. As a result, our understanding of the cellular composition and microenvironment in SAH remains incomplete 8 . > Advances in bioinformatics provide powerful tools to analyze large-scale gene expression data and understand complex biological processes. By integrating transcriptomic data with immune cell infiltration analysis, we can gain a deeper understanding of the molecular mechanisms underlying SAH and identify potential key genes as therapeutic targets 9,10 . Previous studies have indicated that inflammation, oxidative stress, and cell death play crucial roles in the development of SAH, processes that are often closely associated with changes in specific cell types and immune responses 11 . > The goal of this study is to explore the molecular mechanisms of SAH, with a focus on immune cell infiltration and its role in disease progression. We aim to identify key genes and signaling pathways associated with SAH and investigate potential therapeutic strategies. Specifically, we will examine Isorhynchophylline (IRN) as a potential treatment for SAH and analyze its effects on relevant targets and signaling pathways. Through a comprehensive understanding of the pathological features of SAH, this study aims to provide valuable insights into future clinical interventions and treatment strategies.

[17] Pulmonary fibrosis: pathogenesis and therapeutic strategies

Authors: Jianhai Wang, Kuan Li, De Hao, Xue Li, Yu Zhu et al.
Year: 2024
Venue: MedComm
URL: https://www.semanticscholar.org/paper/27d52cce107cbf87fe7b61df145de94a94bc4167
DOI: 10.1002/mco2.744
PMID: 39314887
PMCID: 11417429
Citations: 56
Summary: This review thoroughly examines the diverse etiological factors, cellular and molecular mechanisms, and key signaling pathways involved in PF, such as TGF‐β, WNT/β‐catenin, and PI3K/Akt/mTOR and discusses current therapeutic strategies.
Evidence snippets:
Snippet 1 (score: 0.350) > This review highlights that PF involves multiple factors, including epithelial cells, mesenchymal cells, immune responses, and microorganisms. These elements interact with and modify various pathways simultaneously, necessitating a systematic and integrative research approach. Future research on the mechanisms, diagnostics, and therapies should incorporate advanced technologies, such as single-cell sequencing, organoid cultures, and metabolomics (Figure 3). Single-cell sequencing can be used to identify the unique contributions of specific cell types to the lung microenvironment. Organoid cultures replicate the three-dimensional structure and function of the lung tissue, providing a more physiologically relevant model for studying disease mechanisms and testing treatments. Metabolomics can reveal changes in metabolic pathways that contribute to disease progression, whereas microbiology can elucidate the role of microorganisms in PF. These studies should be integrated within a systems biology framework to capture the intricate interactions and regulatory networks involved in PF. > Early and accurate diagnosis is crucial for effective management of PF. Future efforts should focus on the discovery and clinical application of new biomarkers to detect this disease in its early stages. Advanced imaging techniques and molecular diagnostics can be used to monitor disease progression and evaluate treatment responses. Reliable biomarkers can facilitate personalized treatment strategies, allowing timely and targeted interventions to slow or halt disease progression. > Because of the multifactorial nature of PF, a single therapeutic approach is often inadequate. Therefore, a combination of treatments that target multiple pathways and cellular interactions should be considered. Combining antifibrotic drugs with cell and gene therapies, as well as leveraging nanoparticles and gene-editing technologies, can enhance treatment precision and efficacy. Exploring the synergistic effects of various therapies can improve therapeutic outcomes and reduce adverse effects. Supportive measures such as lifestyle modifications, pulmonary rehabilitation, and oxygen therapy should be incorporated to improve the overall quality of life of patients. > In summary, the pathogenic mechanisms underlying PF are complex and involve numerous cellular interactions and pathways. Future research should adopt a systematic and integrative approach to uncover the intricate details of PF pathogenesis. Early diagnosis using novel biomarkers and advanced imaging techniques coupled with multimodal treatment strategies holds promise for significantly improving patient outcomes.

[18] Clinical Phenotypes of Cardiovascular and Heart Failure Diseases Can Be Reversed? The Holistic Principle of Systems Biology in Multifaceted Heart Diseases

Authors: K. Lourida, G. Louridas
Year: 2022
Venue: Cardiogenetics
URL: https://www.semanticscholar.org/paper/3960806730c4c1115f527e22d6d0a76536570ec5
DOI: 10.3390/cardiogenetics12020015
Citations: 4
Influential citations: 1
Summary: Only by understanding the complexity of chronic heart diseases and explaining the interrelationship between different interconnected biological networks can the probability for clinical phenotypes reversal be increased.
Evidence snippets:
Snippet 1 (score: 0.348) > Treatment with ACEIs, ARBs, and β-blockers impedes deterioration of myocardial function as well as clinical deterioration caused by the deleterious impact of the compensatory systems [58,59]. Therefore, the therapy with ACEIs, ARBs, and β-blockers is the appropriate therapy to block LV remodeling and HF progression and reduce symptoms and/or mortality [55]. > In general, the HF syndrome demonstrates a modular construction with predictable behavior of functional clinical phenotypes having a strong impact on biological networks from epigenetic, cellular to regulatory systems [18]. The importance of individual genes for the pathogenesis and clinical progression of the HF syndrome is restricted to the hypertrophic and dilated cardiomyopathies. It seems that some HF patients have a complex multigenic inheritance, but the importance of individual genes is limited. In contrast, the significant role of epigenetics, proteomics, and metabolomics is increased; but, the complete genetic network system and the interactions between multiomics systems are still uncertain [60]. Multimodal systems that include genetic networks, multiomics, metabolic pathways, environmental factors, and sophisticated disease-related clinical networks are required to be integrated and provide a new holistic and realistic picture. > Significant breakthroughs have been made to understand many of the pathophysiological mechanisms of HFrEF but the natural pathophysiological history and clinical progression of HFpEF still remains inadequately defined [39]. The subclinical progression of pre-clinical diastolic dysfunction (PDD) of LV "to clinical phenotype of HFpEF and the further clinical progression to some more complex clinical models with multi-organ involvement . . . continue to be poorly understood" [40]. Prospective studies are expected to clarify the natural history and clinical progression of HFpEF and define the LV remodeling mechanisms involved. The pathophysiology of LV systolic dysfunction is different to the diastolic dysfunction, as systolic dysfunction is considered a disease of calcium handling and diastolic dysfunction is regarded as a disease of increased myofilament sensitivity to calcium [61][62][63].

[19] Mitochondrial Dysfunction in Diabetes: Shedding Light on a Widespread Oversight

Authors: F. Iheagwam, A. J. Joseph, E. D. Adedoyin, Olawumi Toyin Iheagwam, Samuel Akpoyowvare Ejoh
Year: 2025
Venue: Pathophysiology
URL: https://www.semanticscholar.org/paper/dbf8042761c1a5fc50f8cd894cc498505abac7cb
DOI: 10.3390/pathophysiology32010009
PMID: 39982365
PMCID: 12077258
Citations: 23
Summary: This review aims to elucidate the complex link between mitochondrial dysfunction and diabetes, covering the spectrum of diabetes types, the role of mitochondria in insulin resistance, highlighting pathophysiological mechanisms, mitochondrial DNA damage, and altered mitochondrial biogenesis and dynamics.
Evidence snippets:
Snippet 1 (score: 0.345) > The landscape of DM research is continuously evolving, with emerging technologies and approaches offering new insights into the pathophysiology of the disease and potential therapeutic targets. Advancements in omics technologies, encompassing genomes, transcriptomics, proteomics, and metabolomics, have transformed the molecular mechanisms underlying DM [134]. High-throughput sequencing techniques enable comprehensive analysis of genetic variants, gene expression profiles, protein abundance, and metabolite levels associated with DM and its complications [135]. Single-cell omics approaches provide unprecedented resolution and granularity, allowing researchers to dissect cellular heterogeneity and identify novel cell types, subpopulations, and signalling pathways involved in DM pathogenesis. Integrating multi-omics data sets offers a systems-level perspective of DM, unravelling complex networks of molecular interactions and regulatory circuits underlying disease progression [136]. > In addition to omics technologies, advances in imaging modalities, such as MRI, PET, and optical imaging, enable non-invasive visualisation and quantification of metabolic, functional, and structural changes. Molecular imaging probes targeting specific biomarkers and metabolic pathways provide valuable insights into disease mechanisms and treatment responses in preclinical and clinical settings [85]. Despite significant progress in DM research, numerous unanswered questions and knowledge gaps persist, hindering the ability to develop effective prevention and treatment strategies. Key areas requiring further investigation include the role of epigenetics, environmental factors, and the microbiome in DM susceptibility and progression. Moreover, the interaction between environmental cues and genetic predisposition remains incompletely understood, highlighting the need for comprehensive multi-omics studies and large-scale epidemiological analyses to identify gene-environment interactions and modifiable risk factors for DM [137]. Furthermore, the heterogeneity of DM phenotypes and clinical outcomes poses a challenge for personalised medicine approaches, necessitating robust biomarkers and predictive models to stratify patients based on disease subtypes, prognosis, and treatment response [138].

[20] Increased Longevity and Metabolic Correction Following Syngeneic Bone Marrow Transplantation in a Murine Model of Mucopolysaccharidosis Type I

Authors: D. Wolf, Andrew W. Lenander, Zhenhong Nan, E. Braunlin, Kelly M. Podetz-Pedersen et al.
Year: 2011
Venue: Bone marrow transplantation
URL: https://www.semanticscholar.org/paper/51b7ce35bfb662994b1738c2c69bd35aa5aa54a7
DOI: 10.1038/bmt.2011.239
PMID: 22179554
PMCID: 4465813
Citations: 3
Summary: This murine-transplantation model can be used to evaluate the effects of novel, more effective methods of delivering IDUA to the brain as an adjunct to BMT, and results are similar to those observed in Hurler patients following BMT.
Evidence snippets:
Snippet 1 (score: 0.345) > Mucopolysaccharidosis type I (MPS I) is an autosomal recessive inherited disease caused by deficiency of the glycosidase α-L-iduronidase (IDUA). IDUA is required for the degradation of the glycosaminoglycans (GAG) heparan and dermatan sulfate and deficiency of the enzyme leads to lysosomal accumulation of these substrates (1). MPS 1 affects approximately 1 in 125,000 live human births and homozygosity for specific mutations (e.g., W402X, Q70X) leads to the most severe phenotype, Hurler syndrome (2). Patients with Hurler syndrome develop progressively severe manifestations of the disease within the first year of life, including growth delay, hepatosplenomegaly, skeletal deformities, excess urinary GAG, corneal clouding, and severe neurological deficits. Untreated, these patients usually succumb to the disease in the first decade of life due to complications caused by respiratory infection, cardiac failure, and obstructive airway disease. > Early biochemical research led to discoveries that have provided the basis for treatment of Hurler patients by hematopoeitic stem cell transplantation (HSCT). After synthesis in the endoplasmic reticulum, IDUA is post-translationally modified by the addition of mannose-6 phosphate to Asn residues in the rough endoplasmic reticulum and Golgi apparatus (3). Most of the modified enzyme is sorted and translocated to the lysosomes, but a small proportion of IDUA escapes from the cell into the extracellular environment (4). Extracellular IDUA can then interact with mannose-6-phosphate receptors on the surface of neighboring cells, with subsequent endocytosis, and shuttling to the lysosomes (5-7). IDUA-deficient cells can thus be cleared of accumulated lysosomal GAG through the uptake of IDUA released by non-deficient cells. This cross-corrective mechanism constitutes the basis for development of cellular and molecular strategies to treat this disorder. > Currently, the standard of care for severe Hurler patients involves enzyme replacement therapy (ERT

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No synthesis or second-stage model call is performed.

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Asta Literature Retrieval: Pathophysiology and clinical mechanisms of Hurler syndrome. Core disease mechanisms, molecular and cellular pathways,...

Relevant Papers

[1] Targeting Hepatic Stellate Cells for the Prevention and Treatment of Liver Cirrhosis and Hepatocellular Carcinoma: Strategies and Clinical Translation

[2] Early disease progression of Hurler syndrome

[3] Novel Approaches to Studying SLC13A5 Disease

[4] Musculoskeletal manifestations in mucopolysaccharidosis type I (Hurler syndrome) following hematopoietic stem cell transplantation

[5] Modeling psychiatric disorders: from genomic findings to cellular phenotypes

[6] New therapeutic targets in rare genetic skeletal diseases

[7] Therapies for Mitochondrial Disease: Past, Present, and Future

[8] Building a knowledge graph to enable precision medicine

[9] Human Dermal Fibroblast: A Promising Cellular Model to Study Biological Mechanisms of Major Depression and Antidepressant Drug Response

[10] Effects of SARS-CoV-2 Spike S1 Subunit on the Interplay Between Hepatitis B and Hepatocellular Carcinoma Related Molecular Processes in Human Liver

[11] 18O-assisted dynamic metabolomics for individualized diagnostics and treatment of human diseases

[12] Femoral Structure and Biomechanical Characteristics in Sanfilippo Syndrome Type-B Mice

[13] Progress in the Management of Patients with Cholestatic Liver Disease: Where Are We and Where Are We Going?

[14] Current and Emerging Approaches for Nonalcoholic Steatohepatitis Treatment.

[15] Changes in Serum Proteomic Profiles at Different Stages of Pregnancy Toxemia in Goats

[16] Exploring the molecular mechanisms of subarachnoid hemorrhage and potential therapeutic targets: insights from bioinformatics and drug prediction

[17] Pulmonary fibrosis: pathogenesis and therapeutic strategies

[18] Clinical Phenotypes of Cardiovascular and Heart Failure Diseases Can Be Reversed? The Holistic Principle of Systems Biology in Multifaceted Heart Diseases

[19] Mitochondrial Dysfunction in Diabetes: Shedding Light on a Widespread Oversight

[20] Increased Longevity and Metabolic Correction Following Syngeneic Bone Marrow Transplantation in a Murine Model of Mucopolysaccharidosis Type I

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