Sly syndrome

Mendelian MONDO:0009662 Pathograph 16 Show in embeddings browser Mucopolysaccharidosis Lysosomal Storage Disorder

Sly syndrome, also called mucopolysaccharidosis type VII (MPS VII), is an autosomal recessive lysosomal storage disorder caused by deficiency of beta-glucuronidase (GUSB). Loss of beta-glucuronidase activity blocks lysosomal degradation of the glycosaminoglycans dermatan sulfate, heparan sulfate, and chondroitin sulfate, producing progressive intralysosomal glycosaminoglycan accumulation across many tissues. The clinical spectrum is exceptionally broad: at the severe end MPS VII is one of the classic genetic causes of non-immune hydrops fetalis, while postnatally surviving patients develop multisystem somatic disease (dysostosis multiplex, coarse facies, hepatosplenomegaly, corneal clouding, cardiac valve disease, and short stature) together with variable central nervous system involvement and intellectual disability driven by heparan sulfate storage. Vestronidase alfa (recombinant human beta-glucuronidase) enzyme replacement therapy is approved for MPS VII; hematopoietic stem cell transplantation and supportive care are additional management options.

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1
Mappings
1
Inheritance
6
Pathophys.
8
Phenotypes
16
Pathograph
1
Genes
3
Medical Actions
🔗

Mappings

MONDO
MONDO:0009662 mucopolysaccharidosis type 7
skos:exactMatch MONDO
👪

Inheritance

1
Autosomal recessive inheritance HP:0000007
MPS VII is an autosomal recessive disorder caused by biallelic loss-of-function variants in GUSB.
Autosomal recessive inheritance
Show evidence (1 reference)
PMID:19224584 SUPPORT Human Clinical
"Mucopolysaccharidosis VII (MPS VII; Sly syndrome) is an autosomal recessive disorder caused by a deficiency of beta-glucuronidase (GUS, EC 3.2.1.31; GUSB)."
This GUSB mutation review directly states the autosomal recessive inheritance of MPS VII and the underlying beta-glucuronidase deficiency.
⚙

Pathophysiology

6
Beta-glucuronidase deficiency
Pathogenic GUSB variants reduce or abolish beta-glucuronidase activity, blocking lysosomal degradation of dermatan sulfate, heparan sulfate, and chondroitin sulfate.
GUSB hgnc:4696 ⚠ ABNORMAL
GUSB hgnc:4696
glycosaminoglycan catabolic process GO:0006027 ↓ DECREASED
beta-glucuronidase activity GO:0004566 ↓ DECREASED
Downstream
Lysosomal glycosaminoglycan accumulation Beta-glucuronidase deficiency directly causes progressive intralysosomal storage of its glycosaminoglycan substrates.
Show evidence (1 reference)
PMID:19224584 SUPPORT Human Clinical
"GUS is required to degrade glycosaminoglycans (GAGs), including heparan sulfate (HS), dermatan sulfate (DS), and chondroitin-4,6-sulfate (CS)."
This review states the proximal enzymatic defect: deficient beta-glucuronidase fails to degrade heparan sulfate, dermatan sulfate, and chondroitin sulfate.
Lysosomal glycosaminoglycan accumulation
Beta-glucuronidase insufficiency leads to excess dermatan sulfate, heparan sulfate, and chondroitin sulfate within lysosomes across multiple tissues, creating the primary storage burden that initiates downstream disease biology. The chemical identity of the stored GAGs determines which arms of the mucopolysaccharidosis storage cascade are engaged.
lysosome GO:0005764
Downstream
Heparan sulfate-driven neuroinflammation Stored heparan sulfate engages the neuronopathic arm, producing central nervous system disease.
Dermatan sulfate-driven connective-tissue storage Stored dermatan sulfate (with chondroitin sulfate) engages the somatic connective-tissue arm.
Show evidence (2 references)
PMID:35216110 SUPPORT Other
"Mucopolysaccharidoses are rare paediatric lysosomal storage disorders, characterised by accumulation of glycosaminoglycans within lysosomes"
This cross-MPS review defines intralysosomal GAG accumulation as the characterizing event of the mucopolysaccharidoses, the hub of the storage cascade. Evidence source is OTHER because it is a cross-MPS review.
PMID:19224584 SUPPORT Human Clinical
"GUS is required to degrade glycosaminoglycans (GAGs), including heparan sulfate (HS), dermatan sulfate (DS), and chondroitin-4,6-sulfate (CS)."
Confirms the specific stored GAGs in MPS VII (heparan sulfate, dermatan sulfate, and chondroitin sulfate), the substrate identity that switches on both the neuronopathic and somatic downstream arms.
Heparan sulfate-driven neuroinflammation
Undegraded heparan sulfate accumulates in neurons and microglia and triggers a neuroinflammatory cascade. This is the heparan sulfate-storing arm engaged by MPS VII and the mechanistic basis for the central nervous system involvement and intellectual disability seen in many patients.
neuron CL:0000540 microglial cell CL:0000129
neuroinflammatory response GO:0150076 ↑ INCREASED
Downstream
Progressive central neurodegeneration Sustained heparan sulfate storage and neuroinflammation culminate in progressive central nervous system dysfunction.
Show evidence (1 reference)
PMID:19224584 SUPPORT Human Clinical
"Accumulation of undegraded GAGs in lysosomes of affected tissues leads to mental retardation, short stature, hepatosplenomegaly, bone dysplasia, and hydrops fetalis."
The review links GAG storage (including heparan sulfate) to mental retardation, the central nervous system output of the neuronopathic arm.
Progressive central neurodegeneration
In neuronopathic MPS VII, sustained heparan sulfate storage and neuroinflammation produce progressive central nervous system dysfunction presenting clinically as intellectual disability and developmental delay.
neuron CL:0000540
Downstream
Intellectual disability Central neurodegeneration manifests clinically as intellectual disability in neuronopathic patients.
Show evidence (1 reference)
PMID:35216110 SUPPORT Other
"progressive build-up of sugars may lead to musculoskeletal abnormalities and multi-organ failure, and in others, to cognitive decline"
This cross-MPS review supports cognitive decline as the central nervous system endpoint of the heparan sulfate-storing types. Evidence source is OTHER because it is a cross-MPS review.
Dermatan sulfate-driven connective-tissue storage
Undegraded dermatan sulfate (with chondroitin sulfate) accumulates in connective-tissue fibroblasts and the extracellular matrix of bone, heart valve, cornea, and viscera. This is the somatic arm engaged by MPS VII and produces the connective-tissue phenotype: dysostosis multiplex, corneal clouding, valvular disease, and organomegaly.
fibroblast CL:0000057
extracellular matrix organization GO:0030198 ↕ DYSREGULATED
Downstream
Multisystem somatic disease Progressive connective-tissue and extracellular-matrix storage culminates in multisystem somatic disease, and at the severe end of the spectrum in non-immune hydrops fetalis.
Show evidence (1 reference)
PMID:19224584 SUPPORT Human Clinical
"Accumulation of undegraded GAGs in lysosomes of affected tissues leads to mental retardation, short stature, hepatosplenomegaly, bone dysplasia, and hydrops fetalis."
The review links GAG storage to bone dysplasia, short stature, and hepatosplenomegaly, the connective-tissue/somatic outputs of the dermatan sulfate-storing arm.
Multisystem somatic disease
Accumulated connective-tissue and extracellular-matrix storage produces progressive multisystem somatic disease: dysostosis multiplex, coarse facies, hepatosplenomegaly, corneal clouding, cardiac valve disease, and short stature. In its most severe prenatal form this systemic storage presents as non-immune hydrops fetalis.
fibroblast CL:0000057
Downstream
Hydrops fetalis Severe prenatal multisystem storage can present as non-immune hydrops fetalis.
Dysostosis multiplex Glycosaminoglycan storage in connective tissue, cartilage, and bone produces dysostosis multiplex.
Coarse facial features Connective-tissue storage in craniofacial tissues produces coarse facial features.
Short stature Skeletal and connective-tissue storage contributes to growth failure and short stature.
Hepatosplenomegaly Visceral storage produces liver and spleen enlargement.
Corneal clouding Glycosaminoglycan storage in ocular connective tissue produces corneal opacity.
Abnormal heart valve morphology Glycosaminoglycan storage in cardiac valve extracellular matrix produces valve disease.
Show evidence (2 references)
PMID:35216110 SUPPORT Other
"progressive build-up of sugars may lead to musculoskeletal abnormalities and multi-organ failure, and in others, to cognitive decline"
This cross-MPS review documents progression of GAG storage to musculoskeletal and multi-organ disease, the terminal node of the somatic arm. Evidence source is OTHER because it is a cross-MPS review.
PMID:8831129 SUPPORT Human Clinical
"Vacuolated macrophages were found in all tissues, but were most prominent in placenta, liver, lymph nodes and bone marrow."
This family case series documents the multisystem tissue storage underlying the severe hydropic presentation of MPS VII.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Sly syndrome Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
●

Phenotypes

8
Cardiovascular 2
Hepatosplenomegaly Hepatosplenomegaly HP:0001433
Show evidence (1 reference)
PMID:19224584 SUPPORT Human Clinical
"Accumulation of undegraded GAGs in lysosomes of affected tissues leads to mental retardation, short stature, hepatosplenomegaly, bone dysplasia, and hydrops fetalis."
The review explicitly lists hepatosplenomegaly among the features of MPS VII.
Abnormal heart valve morphology Abnormal heart valve morphology HP:0001654
Show evidence (1 reference)
PMID:19224584 SUPPORT Human Clinical
"Lysosomal storage of GAGs is widespread and affects the brain, skeleton, eye, ear, heart valves, aorta, and the fixed tissue macrophage system."
This GUSB/MPS VII review states that GAG storage affects the heart valves, directly supporting cardiac valve disease as part of the multisystem somatic burden of MPS VII.
Eye 1
Corneal clouding Corneal opacity HP:0007957
Show evidence (1 reference)
PMID:19224584 SUPPORT Human Clinical
"Other findings included facial dysmorphism, plump paws, corneal clouding, granulation of neutrophils, vacuolated lymphocytes, and a positive urine test for sulfated GAGs."
This GUSB/MPS VII review explicitly lists corneal clouding among the clinical findings, directly supporting corneal opacity in MPS VII.
Head and Neck 1
Coarse facial features Coarse facial features HP:0000280
Show evidence (1 reference)
PMID:19224584 SUPPORT Human Clinical
"Other findings included facial dysmorphism, plump paws, corneal clouding, granulation of neutrophils, vacuolated lymphocytes, and a positive urine test for sulfated GAGs."
This GUSB/MPS VII review explicitly lists facial dysmorphism among the clinical findings, directly supporting coarse facial features.
Metabolism 1
Hydrops fetalis Hydrops fetalis HP:0001789
Show evidence (2 references)
PMID:8831129 SUPPORT Human Clinical
"We describe a family case of beta-glucuronidase deficiency with 3 consecutively affected siblings. The three fetuses showed hydrops at a very early stage."
This family case series directly documents non-immune hydrops fetalis as a recurrent prenatal presentation of beta-glucuronidase deficiency (MPS VII).
PMID:9155679 SUPPORT Human Clinical
"A case of mucopolysaccharidosis type VII (MPS VII, beta glucuronidase deficiency) causing fatal hydrops fetalis in the third trimester is presented."
This pathology case report confirms MPS VII as a cause of fatal non-immune hydrops fetalis.
Musculoskeletal 1
Dysostosis multiplex Dysostosis multiplex HP:0000943
Show evidence (1 reference)
PMID:19224584 SUPPORT Human Clinical
"Accumulation of undegraded GAGs in lysosomes of affected tissues leads to mental retardation, short stature, hepatosplenomegaly, bone dysplasia, and hydrops fetalis."
The review lists bone dysplasia (dysostosis multiplex) among the cardinal features of MPS VII.
Nervous System 1
Intellectual disability Intellectual disability HP:0001249
Show evidence (1 reference)
PMID:19224584 SUPPORT Human Clinical
"Accumulation of undegraded GAGs in lysosomes of affected tissues leads to mental retardation, short stature, hepatosplenomegaly, bone dysplasia, and hydrops fetalis."
The review explicitly lists mental retardation (intellectual disability) among the consequences of GAG storage in MPS VII.
Growth 1
Short stature Short stature HP:0004322
Show evidence (1 reference)
PMID:19224584 SUPPORT Human Clinical
"Accumulation of undegraded GAGs in lysosomes of affected tissues leads to mental retardation, short stature, hepatosplenomegaly, bone dysplasia, and hydrops fetalis."
The review explicitly lists short stature among the consequences of GAG storage in MPS VII.
🧬

Genetic Associations

1
GUSB (Pathogenic Variants)
Gene: GUSB hgnc:4696
Show evidence (1 reference)
PMID:19224584 SUPPORT Human Clinical
"We summarize information on the 49 unique, disease-causing mutations determined so far in the GUS gene, including nine novel mutations (eight missense and one splice-site)."
This mutation review documents disease-causing GUSB variants as the molecular cause of MPS VII.
💊

Medical Actions

3
Vestronidase alfa enzyme replacement therapy
Action: Pharmacotherapy NCIT:C15986
Agent: vestronidase alfa NCIT:C152871
Vestronidase alfa (recombinant human beta-glucuronidase, Mepsevii) is the first disease-specific enzyme replacement therapy approved for MPS VII. In a Phase 3 blind-start study it significantly reduced urinary glycosaminoglycan excretion and produced clinical improvement on a multi-domain responder index.
Mechanism Target:
RESTORES Beta-glucuronidase deficiency — Recombinant human beta-glucuronidase supplements the deficient lysosomal enzyme.
Show evidence (1 reference)
PMID:32063397 SUPPORT Human Clinical
"Vestronidase alfa (recombinant human beta-glucuronidase) is an enzyme replacement therapy (ERT) for Mucopolysaccharidosis (MPS) VII, a highly heterogeneous, ultra-rare disease."
This trial identifies vestronidase alfa as recombinant human beta-glucuronidase, supporting replacement of the deficient enzyme.
INHIBITS Lysosomal glycosaminoglycan accumulation — Enzyme replacement lowers glycosaminoglycan storage burden, evidenced by reduced urinary glycosaminoglycan excretion.
Show evidence (1 reference)
PMID:32063397 SUPPORT Human Clinical
"All 12 subjects completed the blind-start study, which showed significantly reduced urinary glycosaminoglycans (GAG) and clinical improvement in a multi-domain responder index"
The trial directly shows that vestronidase alfa lowers urinary GAG, supporting inhibition of the storage mechanism.
Show evidence (1 reference)
PMID:32063397 SUPPORT Human Clinical
"All 12 subjects completed the blind-start study, which showed significantly reduced urinary glycosaminoglycans (GAG) and clinical improvement in a multi-domain responder index"
This long-term study supports biochemical and clinical benefit from vestronidase alfa enzyme replacement therapy in MPS VII.
Hematopoietic stem cell transplantation (HSCT)
Action: hematopoietic stem cell transplantation MAXO:0000747
Hematopoietic stem cell transplantation is an emerging treatment for MPS VII intended to provide donor-derived enzyme activity; it is listed alongside enzyme replacement and gene therapy among current and emerging treatments.
Show evidence (1 reference)
PMID:36578769 SUPPORT Human Clinical
"Besides supportive treatment, current and emerging treatments include enzyme replacement therapy, hematopoietic stem cell transplantation, and gene therapy."
This MPS VII review lists hematopoietic stem cell transplantation among the current and emerging treatments.
Multidisciplinary supportive care
Action: supportive care MAXO:0000950
MPS VII is a multisystem disease requiring ongoing supportive management alongside disease-directed therapy.
Show evidence (1 reference)
PMID:36578769 SUPPORT Human Clinical
"Besides supportive treatment, current and emerging treatments include enzyme replacement therapy, hematopoietic stem cell transplantation, and gene therapy."
This MPS VII review identifies supportive treatment as a component of MPS VII management.
{ }

Source YAML

click to show 
name: Sly syndrome
creation_date: "2026-06-12T00:00:00Z"
category: Mendelian
description: >-
  Sly syndrome, also called mucopolysaccharidosis type VII (MPS VII), is an
  autosomal recessive lysosomal storage disorder caused by deficiency of
  beta-glucuronidase (GUSB). Loss of beta-glucuronidase activity blocks
  lysosomal degradation of the glycosaminoglycans dermatan sulfate, heparan
  sulfate, and chondroitin sulfate, producing progressive intralysosomal
  glycosaminoglycan accumulation across many tissues. The clinical spectrum is
  exceptionally broad: at the severe end MPS VII is one of the classic genetic
  causes of non-immune hydrops fetalis, while postnatally surviving patients
  develop multisystem somatic disease (dysostosis multiplex, coarse facies,
  hepatosplenomegaly, corneal clouding, cardiac valve disease, and short
  stature) together with variable central nervous system involvement and
  intellectual disability driven by heparan sulfate storage. Vestronidase alfa
  (recombinant human beta-glucuronidase) enzyme replacement therapy is approved
  for MPS VII; hematopoietic stem cell transplantation and supportive care are
  additional management options.
disease_term:
  preferred_term: Sly syndrome
  term:
    id: MONDO:0009662
    label: mucopolysaccharidosis type 7
mappings:
  mondo_mappings:
  - term:
      id: MONDO:0009662
      label: mucopolysaccharidosis type 7
    mapping_predicate: skos:exactMatch
    mapping_source: MONDO
parents:
- Mucopolysaccharidosis
- Lysosomal Storage Disorder
synonyms:
- mucopolysaccharidosis type VII
- mucopolysaccharidosis type 7
- MPS VII
- beta-glucuronidase deficiency
- GUSB deficiency
inheritance:
- name: Autosomal recessive inheritance
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    MPS VII is an autosomal recessive disorder caused by biallelic
    loss-of-function variants in GUSB.
  evidence:
  - reference: PMID:19224584
    reference_title: "Mutations and polymorphisms in GUSB gene in mucopolysaccharidosis VII (Sly Syndrome)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Mucopolysaccharidosis VII (MPS VII; Sly syndrome) is an autosomal
      recessive disorder caused by a deficiency of beta-glucuronidase (GUS, EC
      3.2.1.31; GUSB).
    explanation: >-
      This GUSB mutation review directly states the autosomal recessive
      inheritance of MPS VII and the underlying beta-glucuronidase deficiency.
pathophysiology:
- name: Beta-glucuronidase deficiency
  description: >-
    Pathogenic GUSB variants reduce or abolish beta-glucuronidase activity,
    blocking lysosomal degradation of dermatan sulfate, heparan sulfate, and
    chondroitin sulfate.
  gene:
    preferred_term: GUSB
    description: Encodes beta-glucuronidase, the lysosomal hydrolase deficient in Sly syndrome.
    modifier: ABNORMAL
    term:
      id: hgnc:4696
      label: GUSB
  genes:
  - preferred_term: GUSB
    term:
      id: hgnc:4696
      label: GUSB
  molecular_functions:
  - preferred_term: beta-glucuronidase activity
    modifier: DECREASED
    term:
      id: GO:0004566
      label: beta-glucuronidase activity
  biological_processes:
  - preferred_term: glycosaminoglycan catabolic process
    modifier: DECREASED
    term:
      id: GO:0006027
      label: glycosaminoglycan catabolic process
  evidence:
  - reference: PMID:19224584
    reference_title: "Mutations and polymorphisms in GUSB gene in mucopolysaccharidosis VII (Sly Syndrome)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      GUS is required to degrade glycosaminoglycans (GAGs), including heparan
      sulfate (HS), dermatan sulfate (DS), and chondroitin-4,6-sulfate (CS).
    explanation: >-
      This review states the proximal enzymatic defect: deficient
      beta-glucuronidase fails to degrade heparan sulfate, dermatan sulfate, and
      chondroitin sulfate.
  downstream:
  - target: Lysosomal glycosaminoglycan accumulation
    causal_link_type: DIRECT
    description: >-
      Beta-glucuronidase deficiency directly causes progressive intralysosomal
      storage of its glycosaminoglycan substrates.
    evidence:
    - reference: PMID:19224584
      reference_title: "Mutations and polymorphisms in GUSB gene in mucopolysaccharidosis VII (Sly Syndrome)."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Accumulation of undegraded GAGs in lysosomes of affected tissues leads
        to mental retardation, short stature, hepatosplenomegaly, bone
        dysplasia, and hydrops fetalis.
      explanation: >-
        The review links beta-glucuronidase deficiency to lysosomal GAG
        accumulation and its multisystem clinical consequences.
- name: Lysosomal glycosaminoglycan accumulation
  conforms_to: "mps_gag_storage#Lysosomal GAG Accumulation"
  description: >-
    Beta-glucuronidase insufficiency leads to excess dermatan sulfate, heparan
    sulfate, and chondroitin sulfate within lysosomes across multiple tissues,
    creating the primary storage burden that initiates downstream disease
    biology. The chemical identity of the stored GAGs determines which arms of
    the mucopolysaccharidosis storage cascade are engaged.
  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: dermatan sulfate
    term:
      id: CHEBI:18376
      label: dermatan sulfate
    modifier: INCREASED
  - preferred_term: chondroitin sulfate
    term:
      id: CHEBI:37397
      label: chondroitin sulfate
    modifier: INCREASED
  - preferred_term: glycosaminoglycan
    term:
      id: CHEBI:18085
      label: glycosaminoglycan
    modifier: INCREASED
  evidence:
  - reference: PMID:35216110
    reference_title: "The Mucopolysaccharidoses."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Mucopolysaccharidoses are rare paediatric lysosomal storage disorders, characterised by accumulation of glycosaminoglycans within lysosomes"
    explanation: >-
      This cross-MPS review defines intralysosomal GAG accumulation as the
      characterizing event of the mucopolysaccharidoses, the hub of the storage
      cascade. Evidence source is OTHER because it is a cross-MPS review.
  - reference: PMID:19224584
    reference_title: "Mutations and polymorphisms in GUSB gene in mucopolysaccharidosis VII (Sly Syndrome)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      GUS is required to degrade glycosaminoglycans (GAGs), including heparan
      sulfate (HS), dermatan sulfate (DS), and chondroitin-4,6-sulfate (CS).
    explanation: >-
      Confirms the specific stored GAGs in MPS VII (heparan sulfate, dermatan
      sulfate, and chondroitin sulfate), the substrate identity that switches on
      both the neuronopathic and somatic downstream arms.
  downstream:
  - target: Heparan sulfate-driven neuroinflammation
    causal_link_type: DIRECT
    description: >-
      Stored heparan sulfate engages the neuronopathic arm, producing central
      nervous system disease.
  - target: Dermatan sulfate-driven connective-tissue storage
    causal_link_type: DIRECT
    description: >-
      Stored dermatan sulfate (with chondroitin sulfate) engages the somatic
      connective-tissue arm.
- name: Heparan sulfate-driven neuroinflammation
  conforms_to: "mps_gag_storage#Heparan Sulfate-Driven Neuroinflammation"
  description: >-
    Undegraded heparan sulfate accumulates in neurons and microglia and triggers
    a neuroinflammatory cascade. This is the heparan sulfate-storing arm engaged
    by MPS VII and the mechanistic basis for the central nervous system
    involvement and intellectual disability seen in many patients.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  - preferred_term: microglial cell
    term:
      id: CL:0000129
      label: microglial cell
  biological_processes:
  - preferred_term: neuroinflammatory response
    term:
      id: GO:0150076
      label: neuroinflammatory response
    modifier: INCREASED
  evidence:
  - reference: PMID:19224584
    reference_title: "Mutations and polymorphisms in GUSB gene in mucopolysaccharidosis VII (Sly Syndrome)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Accumulation of undegraded GAGs in lysosomes of affected tissues leads
      to mental retardation, short stature, hepatosplenomegaly, bone
      dysplasia, and hydrops fetalis.
    explanation: >-
      The review links GAG storage (including heparan sulfate) to mental
      retardation, the central nervous system output of the neuronopathic arm.
  downstream:
  - target: Progressive central neurodegeneration
    causal_link_type: DIRECT
    description: >-
      Sustained heparan sulfate storage and neuroinflammation culminate in
      progressive central nervous system dysfunction.
    evidence:
    - reference: PMID:35216110
      reference_title: "The Mucopolysaccharidoses."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "progressive build-up of sugars may lead to musculoskeletal abnormalities and multi-organ failure, and in others, to cognitive decline"
      explanation: >-
        This cross-MPS review documents the heparan sulfate-storing types
        progressing to cognitive decline. Evidence source is OTHER because it is
        a cross-MPS review.
- name: Progressive central neurodegeneration
  conforms_to: "mps_gag_storage#Progressive Central Neurodegeneration"
  description: >-
    In neuronopathic MPS VII, sustained heparan sulfate storage and
    neuroinflammation produce progressive central nervous system dysfunction
    presenting clinically as intellectual disability and developmental delay.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  evidence:
  - reference: PMID:35216110
    reference_title: "The Mucopolysaccharidoses."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "progressive build-up of sugars may lead to musculoskeletal abnormalities and multi-organ failure, and in others, to cognitive decline"
    explanation: >-
      This cross-MPS review supports cognitive decline as the central nervous
      system endpoint of the heparan sulfate-storing types. Evidence source is
      OTHER because it is a cross-MPS review.
  downstream:
  - target: Intellectual disability
    causal_link_type: DIRECT
    description: >-
      Central neurodegeneration manifests clinically as intellectual disability
      in neuronopathic patients.
    evidence:
    - reference: PMID:19224584
      reference_title: "Mutations and polymorphisms in GUSB gene in mucopolysaccharidosis VII (Sly Syndrome)."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Accumulation of undegraded GAGs in lysosomes of affected tissues leads
        to mental retardation, short stature, hepatosplenomegaly, bone
        dysplasia, and hydrops fetalis.
      explanation: >-
        The review explicitly lists mental retardation among the consequences of
        GAG storage in MPS VII.
- name: Dermatan sulfate-driven connective-tissue storage
  conforms_to: "mps_gag_storage#Dermatan Sulfate-Driven Connective-Tissue and ECM Storage"
  description: >-
    Undegraded dermatan sulfate (with chondroitin sulfate) accumulates in
    connective-tissue fibroblasts and the extracellular matrix of bone, heart
    valve, cornea, and viscera. This is the somatic arm engaged by MPS VII and
    produces the connective-tissue phenotype: dysostosis multiplex, corneal
    clouding, valvular disease, and organomegaly.
  cell_types:
  - preferred_term: fibroblast
    term:
      id: CL:0000057
      label: fibroblast
  biological_processes:
  - preferred_term: extracellular matrix organization
    term:
      id: GO:0030198
      label: extracellular matrix organization
    modifier: DYSREGULATED
  evidence:
  - reference: PMID:19224584
    reference_title: "Mutations and polymorphisms in GUSB gene in mucopolysaccharidosis VII (Sly Syndrome)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Accumulation of undegraded GAGs in lysosomes of affected tissues leads
      to mental retardation, short stature, hepatosplenomegaly, bone
      dysplasia, and hydrops fetalis.
    explanation: >-
      The review links GAG storage to bone dysplasia, short stature, and
      hepatosplenomegaly, the connective-tissue/somatic outputs of the dermatan
      sulfate-storing arm.
  downstream:
  - target: Multisystem somatic disease
    causal_link_type: DIRECT
    description: >-
      Progressive connective-tissue and extracellular-matrix storage culminates
      in multisystem somatic disease, and at the severe end of the spectrum in
      non-immune hydrops fetalis.
    evidence:
    - reference: PMID:9155679
      reference_title: "Mucopolysaccharidosis type VII associated with hydrops fetalis: histopathological and ultrastructural features with genetic implications."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        A case of mucopolysaccharidosis type VII (MPS VII, beta glucuronidase
        deficiency) causing fatal hydrops fetalis in the third trimester is
        presented.
      explanation: >-
        This case report documents severe systemic storage presenting
        prenatally as non-immune hydrops fetalis, the most severe somatic
        endpoint of MPS VII.
- name: Multisystem somatic disease
  conforms_to: "mps_gag_storage#Multisystem Somatic Disease"
  description: >-
    Accumulated connective-tissue and extracellular-matrix storage produces
    progressive multisystem somatic disease: dysostosis multiplex, coarse
    facies, hepatosplenomegaly, corneal clouding, cardiac valve disease, and
    short stature. In its most severe prenatal form this systemic storage
    presents as non-immune hydrops fetalis.
  cell_types:
  - preferred_term: fibroblast
    term:
      id: CL:0000057
      label: fibroblast
  evidence:
  - reference: PMID:35216110
    reference_title: "The Mucopolysaccharidoses."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "progressive build-up of sugars may lead to musculoskeletal abnormalities and multi-organ failure, and in others, to cognitive decline"
    explanation: >-
      This cross-MPS review documents progression of GAG storage to
      musculoskeletal and multi-organ disease, the terminal node of the somatic
      arm. Evidence source is OTHER because it is a cross-MPS review.
  - reference: PMID:8831129
    reference_title: "Non-immune hydrops fetalis caused by beta-glucuronidase deficiency (mucopolysaccharidosis VII). Study of a family with 3 affected siblings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Vacuolated macrophages were found in all tissues, but were most prominent in placenta, liver, lymph nodes and bone marrow."
    explanation: >-
      This family case series documents the multisystem tissue storage
      underlying the severe hydropic presentation of MPS VII.
  downstream:
  - target: Hydrops fetalis
    causal_link_type: DIRECT
    description: >-
      Severe prenatal multisystem storage can present as non-immune hydrops
      fetalis.
    evidence:
    - reference: PMID:9155679
      reference_title: "Mucopolysaccharidosis type VII associated with hydrops fetalis: histopathological and ultrastructural features with genetic implications."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        A case of mucopolysaccharidosis type VII (MPS VII, beta glucuronidase
        deficiency) causing fatal hydrops fetalis in the third trimester is
        presented.
      explanation: >-
        This case report links severe MPS VII multisystem storage to hydrops
        fetalis.
  - target: Dysostosis multiplex
    causal_link_type: DIRECT
    description: >-
      Glycosaminoglycan storage in connective tissue, cartilage, and bone
      produces dysostosis multiplex.
    evidence:
    - reference: PMID:19224584
      reference_title: "Mutations and polymorphisms in GUSB gene in mucopolysaccharidosis VII (Sly Syndrome)."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Accumulation of undegraded GAGs in lysosomes of affected tissues leads
        to mental retardation, short stature, hepatosplenomegaly, bone
        dysplasia, and hydrops fetalis.
      explanation: >-
        The MPS VII review lists bone dysplasia among the downstream outcomes
        of GAG accumulation.
  - target: Coarse facial features
    causal_link_type: DIRECT
    description: >-
      Connective-tissue storage in craniofacial tissues produces coarse facial
      features.
    evidence:
    - reference: ORPHA:584
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "HP:0000280 | Coarse facial features | Very frequent (99-80%)"
      explanation: Orphadata lists coarse facial features as a very frequent MPS VII phenotype.
  - target: Short stature
    causal_link_type: DIRECT
    description: >-
      Skeletal and connective-tissue storage contributes to growth failure and
      short stature.
    evidence:
    - reference: PMID:19224584
      reference_title: "Mutations and polymorphisms in GUSB gene in mucopolysaccharidosis VII (Sly Syndrome)."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Accumulation of undegraded GAGs in lysosomes of affected tissues leads
        to mental retardation, short stature, hepatosplenomegaly, bone
        dysplasia, and hydrops fetalis.
      explanation: >-
        The MPS VII review lists short stature among the downstream outcomes of
        GAG accumulation.
  - target: Hepatosplenomegaly
    causal_link_type: DIRECT
    description: >-
      Visceral storage produces liver and spleen enlargement.
    evidence:
    - reference: PMID:19224584
      reference_title: "Mutations and polymorphisms in GUSB gene in mucopolysaccharidosis VII (Sly Syndrome)."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Accumulation of undegraded GAGs in lysosomes of affected tissues leads
        to mental retardation, short stature, hepatosplenomegaly, bone
        dysplasia, and hydrops fetalis.
      explanation: >-
        The MPS VII review lists hepatosplenomegaly among the downstream
        outcomes of GAG accumulation.
  - target: Corneal clouding
    causal_link_type: DIRECT
    description: >-
      Glycosaminoglycan storage in ocular connective tissue produces corneal
      opacity.
    evidence:
    - reference: ORPHA:584
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "HP:0007957 | Corneal opacity | Very frequent (99-80%)"
      explanation: Orphadata lists corneal opacity as a very frequent MPS VII phenotype.
  - target: Abnormal heart valve morphology
    causal_link_type: DIRECT
    description: >-
      Glycosaminoglycan storage in cardiac valve extracellular matrix produces
      valve disease.
    evidence:
    - reference: ORPHA:584
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "cardiac valve disease"
      explanation: Orphadata definition lists cardiac valve disease among the most consistent MPS VII features.
phenotypes:
- name: Hydrops fetalis
  category: Prenatal
  description: >-
    Non-immune hydrops fetalis is a notable and somewhat distinctive
    presentation of severe MPS VII, reflecting massive prenatal systemic
    glycosaminoglycan storage. MPS VII is one of the classic genetic lysosomal
    causes of non-immune hydrops fetalis.
  phenotype_term:
    preferred_term: Hydrops fetalis
    term:
      id: HP:0001789
      label: Hydrops fetalis
  evidence:
  - reference: PMID:8831129
    reference_title: "Non-immune hydrops fetalis caused by beta-glucuronidase deficiency (mucopolysaccharidosis VII). Study of a family with 3 affected siblings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We describe a family case of beta-glucuronidase deficiency with 3
      consecutively affected siblings. The three fetuses showed hydrops at a
      very early stage.
    explanation: >-
      This family case series directly documents non-immune hydrops fetalis as a
      recurrent prenatal presentation of beta-glucuronidase deficiency (MPS VII).
  - reference: PMID:9155679
    reference_title: "Mucopolysaccharidosis type VII associated with hydrops fetalis: histopathological and ultrastructural features with genetic implications."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A case of mucopolysaccharidosis type VII (MPS VII, beta glucuronidase
      deficiency) causing fatal hydrops fetalis in the third trimester is
      presented.
    explanation: >-
      This pathology case report confirms MPS VII as a cause of fatal non-immune
      hydrops fetalis.
- name: Dysostosis multiplex
  category: Skeletal
  description: >-
    Dysostosis multiplex (bone dysplasia) is a cardinal skeletal feature of MPS
    VII, reflecting glycosaminoglycan storage in cartilage and bone.
  phenotype_term:
    preferred_term: Dysostosis multiplex
    term:
      id: HP:0000943
      label: Dysostosis multiplex
  evidence:
  - reference: PMID:19224584
    reference_title: "Mutations and polymorphisms in GUSB gene in mucopolysaccharidosis VII (Sly Syndrome)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Accumulation of undegraded GAGs in lysosomes of affected tissues leads
      to mental retardation, short stature, hepatosplenomegaly, bone
      dysplasia, and hydrops fetalis.
    explanation: >-
      The review lists bone dysplasia (dysostosis multiplex) among the cardinal
      features of MPS VII.
- name: Coarse facial features
  category: Craniofacial
  description: >-
    Progressive coarsening of facial appearance is a characteristic somatic
    feature of MPS VII shared with other mucopolysaccharidoses.
  phenotype_term:
    preferred_term: Coarse facial features
    term:
      id: HP:0000280
      label: Coarse facial features
  evidence:
  - reference: PMID:19224584
    reference_title: "Mutations and polymorphisms in GUSB gene in mucopolysaccharidosis VII (Sly Syndrome)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Other findings included facial dysmorphism, plump paws, corneal clouding,
      granulation of neutrophils, vacuolated lymphocytes, and a positive urine
      test for sulfated GAGs.
    explanation: >-
      This GUSB/MPS VII review explicitly lists facial dysmorphism among the
      clinical findings, directly supporting coarse facial features.
- name: Short stature
  category: Growth
  description: >-
    Growth failure develops as connective-tissue and skeletal disease
    progresses.
  phenotype_term:
    preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  evidence:
  - reference: PMID:19224584
    reference_title: "Mutations and polymorphisms in GUSB gene in mucopolysaccharidosis VII (Sly Syndrome)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Accumulation of undegraded GAGs in lysosomes of affected tissues leads
      to mental retardation, short stature, hepatosplenomegaly, bone
      dysplasia, and hydrops fetalis.
    explanation: >-
      The review explicitly lists short stature among the consequences of GAG
      storage in MPS VII.
- name: Hepatosplenomegaly
  category: Gastrointestinal
  description: >-
    Increased liver and spleen volume is part of the multisystem visceral
    storage burden of MPS VII.
  phenotype_term:
    preferred_term: Hepatosplenomegaly
    term:
      id: HP:0001433
      label: Hepatosplenomegaly
  evidence:
  - reference: PMID:19224584
    reference_title: "Mutations and polymorphisms in GUSB gene in mucopolysaccharidosis VII (Sly Syndrome)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Accumulation of undegraded GAGs in lysosomes of affected tissues leads
      to mental retardation, short stature, hepatosplenomegaly, bone
      dysplasia, and hydrops fetalis.
    explanation: >-
      The review explicitly lists hepatosplenomegaly among the features of MPS
      VII.
- name: Corneal clouding
  category: Ophthalmologic
  description: >-
    Corneal opacity (corneal clouding) reflects glycosaminoglycan storage in the
    corneal stroma and is part of the somatic phenotype of MPS VII.
  phenotype_term:
    preferred_term: Corneal clouding
    term:
      id: HP:0007957
      label: Corneal opacity
  evidence:
  - reference: PMID:19224584
    reference_title: "Mutations and polymorphisms in GUSB gene in mucopolysaccharidosis VII (Sly Syndrome)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Other findings included facial dysmorphism, plump paws, corneal clouding,
      granulation of neutrophils, vacuolated lymphocytes, and a positive urine
      test for sulfated GAGs.
    explanation: >-
      This GUSB/MPS VII review explicitly lists corneal clouding among the
      clinical findings, directly supporting corneal opacity in MPS VII.
- name: Intellectual disability
  category: Neurologic
  description: >-
    Intellectual disability (mental retardation) occurs in neuronopathic MPS VII
    and reflects heparan sulfate-driven central nervous system disease.
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  evidence:
  - reference: PMID:19224584
    reference_title: "Mutations and polymorphisms in GUSB gene in mucopolysaccharidosis VII (Sly Syndrome)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Accumulation of undegraded GAGs in lysosomes of affected tissues leads
      to mental retardation, short stature, hepatosplenomegaly, bone
      dysplasia, and hydrops fetalis.
    explanation: >-
      The review explicitly lists mental retardation (intellectual disability)
      among the consequences of GAG storage in MPS VII.
- name: Abnormal heart valve morphology
  category: Cardiovascular
  description: >-
    Cardiac valve disease arises from glycosaminoglycan storage in valve
    extracellular matrix, part of the multisystem somatic burden of MPS VII.
  phenotype_term:
    preferred_term: Abnormal heart valve morphology
    term:
      id: HP:0001654
      label: Abnormal heart valve morphology
  evidence:
  - reference: PMID:19224584
    reference_title: "Mutations and polymorphisms in GUSB gene in mucopolysaccharidosis VII (Sly Syndrome)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Lysosomal storage of GAGs is widespread and affects the brain, skeleton,
      eye, ear, heart valves, aorta, and the fixed tissue macrophage system.
    explanation: >-
      This GUSB/MPS VII review states that GAG storage affects the heart valves,
      directly supporting cardiac valve disease as part of the multisystem
      somatic burden of MPS VII.
genetic:
- name: GUSB
  gene_term:
    preferred_term: GUSB
    term:
      id: hgnc:4696
      label: GUSB
  association: Pathogenic Variants
  evidence:
  - reference: PMID:19224584
    reference_title: "Mutations and polymorphisms in GUSB gene in mucopolysaccharidosis VII (Sly Syndrome)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We summarize information on the 49 unique, disease-causing mutations
      determined so far in the GUS gene, including nine novel mutations (eight
      missense and one splice-site).
    explanation: >-
      This mutation review documents disease-causing GUSB variants as the
      molecular cause of MPS VII.
treatments:
- name: Vestronidase alfa enzyme replacement therapy
  description: >-
    Vestronidase alfa (recombinant human beta-glucuronidase, Mepsevii) is the
    first disease-specific enzyme replacement therapy approved for MPS VII. In a
    Phase 3 blind-start study it significantly reduced urinary glycosaminoglycan
    excretion and produced clinical improvement on a multi-domain responder
    index.
  therapeutic_modality: PROTEIN_REPLACEMENT
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: vestronidase alfa
      term:
        id: NCIT:C152871
        label: Vestronidase Alfa
  target_mechanisms:
  - target: Beta-glucuronidase deficiency
    treatment_effect: RESTORES
    description: >-
      Recombinant human beta-glucuronidase supplements the deficient lysosomal
      enzyme.
    evidence:
    - reference: PMID:32063397
      reference_title: "The long-term safety and efficacy of vestronidase alfa, rhGUS enzyme replacement therapy, in subjects with mucopolysaccharidosis VII."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Vestronidase alfa (recombinant human beta-glucuronidase) is an enzyme
        replacement therapy (ERT) for Mucopolysaccharidosis (MPS) VII, a highly
        heterogeneous, ultra-rare disease.
      explanation: >-
        This trial identifies vestronidase alfa as recombinant human
        beta-glucuronidase, supporting replacement of the deficient enzyme.
  - target: Lysosomal glycosaminoglycan accumulation
    treatment_effect: INHIBITS
    description: >-
      Enzyme replacement lowers glycosaminoglycan storage burden, evidenced by
      reduced urinary glycosaminoglycan excretion.
    evidence:
    - reference: PMID:32063397
      reference_title: "The long-term safety and efficacy of vestronidase alfa, rhGUS enzyme replacement therapy, in subjects with mucopolysaccharidosis VII."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        All 12 subjects completed the blind-start study, which showed
        significantly reduced urinary glycosaminoglycans (GAG) and clinical
        improvement in a multi-domain responder index
      explanation: >-
        The trial directly shows that vestronidase alfa lowers urinary GAG,
        supporting inhibition of the storage mechanism.
  evidence:
  - reference: PMID:32063397
    reference_title: "The long-term safety and efficacy of vestronidase alfa, rhGUS enzyme replacement therapy, in subjects with mucopolysaccharidosis VII."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All 12 subjects completed the blind-start study, which showed
      significantly reduced urinary glycosaminoglycans (GAG) and clinical
      improvement in a multi-domain responder index
    explanation: >-
      This long-term study supports biochemical and clinical benefit from
      vestronidase alfa enzyme replacement therapy in MPS VII.
- name: Hematopoietic stem cell transplantation (HSCT)
  description: >-
    Hematopoietic stem cell transplantation is an emerging treatment for MPS VII
    intended to provide donor-derived enzyme activity; it is listed alongside
    enzyme replacement and gene therapy among current and emerging treatments.
  treatment_term:
    preferred_term: hematopoietic stem cell transplantation
    term:
      id: MAXO:0000747
      label: hematopoietic stem cell transplantation
  evidence:
  - reference: PMID:36578769
    reference_title: "Diagnosis and Emerging Treatment Strategies for Mucopolysaccharidosis VII (Sly Syndrome)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Besides supportive treatment, current and emerging treatments include
      enzyme replacement therapy, hematopoietic stem cell transplantation, and
      gene therapy.
    explanation: >-
      This MPS VII review lists hematopoietic stem cell transplantation among
      the current and emerging treatments.
- name: Multidisciplinary supportive care
  description: >-
    MPS VII is a multisystem disease requiring ongoing supportive management
    alongside disease-directed therapy.
  treatment_term:
    preferred_term: supportive care
    term:
      id: MAXO:0000950
      label: supportive care
  evidence:
  - reference: PMID:36578769
    reference_title: "Diagnosis and Emerging Treatment Strategies for Mucopolysaccharidosis VII (Sly Syndrome)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Besides supportive treatment, current and emerging treatments include
      enzyme replacement therapy, hematopoietic stem cell transplantation, and
      gene therapy.
    explanation: >-
      This MPS VII review identifies supportive treatment as a component of MPS
      VII management.