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1
Mappings
1
Definitions
1
Inheritance
2
Pathophys.
2
Phenotypes
5
Pathograph
1
Genes
1
Medical Actions
1
Differentials
1
Deep Research
🔗

Mappings

MONDO
MONDO:0012517 Gaucher disease due to saposin C deficiency
skos:exactMatch MONDO
Primary MONDO disease identifier for this saposin C deficiency Gaucher disease entry.
📘

Definitions

1
Clinical case definition of saposin C deficiency Gaucher disease
Gaucher disease due to saposin C deficiency is an atypical Gaucher disease defined by biallelic PSAP variants abolishing the saposin C activator, with glucosylceramide accumulation and a Gaucher-like phenotype despite normal glucocerebrosidase enzyme activity.
CASE_DEFINITION Disease-level case definition for saposin C deficiency Gaucher disease.
Show evidence (1 reference)
PMID:17919309 SUPPORT Human Clinical
"Saposin (SAP-) C is required for glucosylceramide degradation, and its deficiency results in a variant form of Gaucher disease."
Anchors the case definition in saposin C deficiency causing variant Gaucher disease.
👪

Inheritance

1
Autosomal recessive HP:0000007
Autosomal recessive inheritance
Show evidence (1 reference)
PMID:35456468 SUPPORT Human Clinical
"A homozygous missense variant c.1076A>C: p.(Glu359Ala) in exon 10 of the PSAP"
A homozygous PSAP variant in affected siblings indicates autosomal recessive inheritance.

Pathophysiology

2
Saposin C Deficiency from PSAP Variants
Saposin C arises from proteolytic cleavage of prosaposin (encoded by PSAP). Biallelic PSAP variants abolish saposin C, the activator protein that glucocerebrosidase requires to access and degrade glucosylceramide. Enzyme and GBA1 gene are normal; the defect is a missing activator cofactor.
macrophage CL:0000235
PSAP hgnc:9498
Show evidence (2 references)
PMID:38928321 SUPPORT Human Clinical
"Glucocerebrosidase (GCase) is a lysosomal enzyme that catalyzes the breakdown of glucosylceramide in the presence of its activator saposin C (SapC)."
Glucocerebrosidase requires the saposin C activator (from PSAP) to degrade glucosylceramide.
PMID:17919309 SUPPORT Human Clinical
"Saposin (SAP-) C is required for glucosylceramide degradation, and its deficiency results in a variant form of Gaucher disease."
Saposin C deficiency causes a variant form of Gaucher disease.
Lysosomal Glucosylceramide Accumulation
Undegraded glucosylceramide accumulates in macrophage lysosomes, producing lipid-laden storage macrophages (Gaucher-like cells) in the reticuloendothelial system.
macrophage CL:0000235
glucosylceramide catabolic process GO:0006680 ↓ DECREASED
lysosome GO:0005764
Show evidence (1 reference)
PMID:38928321 SUPPORT Human Clinical
"impairment of GCase activity can be rarely caused by SapC or LIMP-2 deficiencies"
Saposin C deficiency impairs glucocerebrosidase function, causing glucosylceramide accumulation.

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Gaucher Disease Due To Saposin C Deficiency 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

2
Blood 1
Thrombocytopenia Thrombocytopenia HP:0001873
Show evidence (1 reference)
PMID:35456468 SUPPORT Human Clinical
"hepatosplenomegaly, kyphosis, and thrombocytopenia"
Thrombocytopenia is part of the atypical Gaucher phenotype.
Cardiovascular 1
Hepatosplenomegaly Hepatosplenomegaly HP:0001433
Show evidence (1 reference)
PMID:35456468 SUPPORT Human Clinical
"hepatosplenomegaly, kyphosis, and thrombocytopenia"
Hepatosplenomegaly is a feature of atypical Gaucher disease from PSAP variants.
🧬

Genetic Associations

1
PSAP (Biallelic PSAP variants abolishing saposin C)
Gene: PSAP hgnc:9498 relationship_type: CAUSATIVE variant_origin: GERMLINE
Show evidence (1 reference)
PMID:35456468 SUPPORT Human Clinical
"Atypical Gaucher disease is caused by variants in the PSAP gene."
PSAP variants cause atypical (saposin C deficiency) Gaucher disease.
💊

Medical Actions

1
Supportive Care
Action: Supportive Care NCIT:C15747
No saposin-C-specific disease-modifying therapy is established; management is supportive and symptomatic, drawing on approaches used for classic Gaucher disease.
🔀

Differential Diagnoses

1

Conditions with similar clinical presentations that must be differentiated from Gaucher Disease Due To Saposin C Deficiency:

Overlapping Features Classic Gaucher disease caused by glucocerebrosidase (GBA1) deficiency, with the same glucosylceramide storage but a deficient enzyme.
Distinguishing Features
  • Caused by deficient glucocerebrosidase enzyme activity (GBA1), whereas saposin C deficiency leaves enzyme activity normal.
Show evidence (1 reference)
PMID:38928321 SUPPORT Human Clinical
"GCase deficiency causes Gaucher Disease (GD), which is mainly due to biallelic pathogenetic variants in the GCase-encoding gene, GBA1."
Classic Gaucher disease is GBA1 enzyme deficiency, distinct from the saposin C cofactor defect.
{ }

Source YAML

click to show
name: Gaucher Disease Due To Saposin C Deficiency
creation_date: "2026-06-13T00:00:00Z"
description: >-
  Gaucher disease due to saposin C deficiency is a rare atypical Gaucher disease caused by
  biallelic PSAP variants that abolish saposin C, the lysosomal sphingolipid activator
  protein required by glucocerebrosidase (GCase) to degrade glucosylceramide. Although the
  glucocerebrosidase gene (GBA1) and enzyme are normal, the missing cofactor leads to
  glucosylceramide accumulation in macrophages, producing a Gaucher-like phenotype with
  hepatosplenomegaly, thrombocytopenia, and (in some patients) neurological involvement.
category: Mendelian
disease_term:
  preferred_term: Gaucher disease due to saposin C deficiency
  term:
    id: MONDO:0012517
    label: Gaucher disease due to saposin C deficiency
mappings:
  mondo_mappings:
  - term:
      id: MONDO:0012517
      label: Gaucher disease due to saposin C deficiency
    mapping_predicate: skos:exactMatch
    mapping_source: MONDO
    mapping_justification: Primary MONDO disease identifier for this saposin C deficiency Gaucher disease entry.
synonyms:
- Atypical Gaucher disease due to saposin C deficiency
- Saposin C deficiency
- Gaucher disease, variant due to SAP-C deficiency
parents:
- Sphingolipidosis
- Lysosomal Storage Disorder
pathophysiology:
- name: Saposin C Deficiency from PSAP Variants
  conforms_to: "lysosomal_substrate_accumulation#Lysosomal Hydrolase or Cofactor Deficiency"
  description: >-
    Saposin C arises from proteolytic cleavage of prosaposin (encoded by PSAP). Biallelic
    PSAP variants abolish saposin C, the activator protein that glucocerebrosidase requires
    to access and degrade glucosylceramide. Enzyme and GBA1 gene are normal; the defect is
    a missing activator cofactor.
  gene:
    preferred_term: PSAP
    term:
      id: hgnc:9498
      label: PSAP
  cell_types:
  - preferred_term: macrophage
    term:
      id: CL:0000235
      label: macrophage
  evidence:
  - reference: PMID:38928321
    reference_title: "Deficiency of Glucocerebrosidase Activity beyond Gaucher Disease: PSAP and LIMP-2 Dysfunctions."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Glucocerebrosidase (GCase) is a lysosomal enzyme that catalyzes the breakdown of glucosylceramide in the presence of its activator saposin C (SapC)."
    explanation: "Glucocerebrosidase requires the saposin C activator (from PSAP) to degrade glucosylceramide."
  - reference: PMID:17919309
    reference_title: "Non-neuronopathic Gaucher disease due to saposin C deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Saposin (SAP-) C is required for glucosylceramide degradation, and its deficiency results in a variant form of Gaucher disease."
    explanation: "Saposin C deficiency causes a variant form of Gaucher disease."
  downstream:
  - target: Lysosomal Glucosylceramide Accumulation
    description: Without the activator, glucosylceramide cannot be degraded and accumulates.
- name: Lysosomal Glucosylceramide Accumulation
  conforms_to: "lysosomal_substrate_accumulation#Lysosomal Substrate Accumulation"
  description: >-
    Undegraded glucosylceramide accumulates in macrophage lysosomes, producing
    lipid-laden storage macrophages (Gaucher-like cells) in the reticuloendothelial system.
  cell_types:
  - preferred_term: macrophage
    term:
      id: CL:0000235
      label: macrophage
  cellular_components:
  - preferred_term: lysosome
    term:
      id: GO:0005764
      label: lysosome
  biological_processes:
  - preferred_term: glucosylceramide catabolic process
    modifier: DECREASED
    term:
      id: GO:0006680
      label: glucosylceramide catabolic process
  evidence:
  - reference: PMID:38928321
    reference_title: "Deficiency of Glucocerebrosidase Activity beyond Gaucher Disease: PSAP and LIMP-2 Dysfunctions."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "impairment of GCase activity can be rarely caused by SapC or LIMP-2 deficiencies"
    explanation: "Saposin C deficiency impairs glucocerebrosidase function, causing glucosylceramide accumulation."
  downstream:
  - target: Hepatosplenomegaly
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - lipid-laden storage macrophages in the reticuloendothelial system
    - visceral organ infiltration
    description: Glucosylceramide storage in macrophages produces Gaucher-like reticuloendothelial infiltration and hepatosplenomegaly.
    evidence:
    - reference: PMID:35456468
      reference_title: "Phenotype Expansion for Atypical Gaucher Disease Due to Homozygous Missense PSAP Variant in a Large Consanguineous Pakistani Family."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "hepatosplenomegaly, kyphosis, and thrombocytopenia"
      explanation: This case-family report documents hepatosplenomegaly in PSAP-related Gaucher disease.
  - target: Thrombocytopenia
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Gaucher-like reticuloendothelial storage
    - hypersplenism and marrow involvement
    description: Reticuloendothelial and marrow storage disease can reduce circulating platelets.
    evidence:
    - reference: PMID:35456468
      reference_title: "Phenotype Expansion for Atypical Gaucher Disease Due to Homozygous Missense PSAP Variant in a Large Consanguineous Pakistani Family."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "hepatosplenomegaly, kyphosis, and thrombocytopenia"
      explanation: This case-family report documents thrombocytopenia in PSAP-related Gaucher disease.
phenotypes:
- name: Hepatosplenomegaly
  description: Visceral organomegaly from glucosylceramide-laden storage macrophages.
  phenotype_term:
    preferred_term: Hepatosplenomegaly
    term:
      id: HP:0001433
      label: Hepatosplenomegaly
  evidence:
  - reference: PMID:35456468
    reference_title: "Phenotype Expansion for Atypical Gaucher Disease Due to Homozygous Missense PSAP Variant in a Large Consanguineous Pakistani Family."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "hepatosplenomegaly, kyphosis, and thrombocytopenia"
    explanation: "Hepatosplenomegaly is a feature of atypical Gaucher disease from PSAP variants."
- name: Thrombocytopenia
  description: Thrombocytopenia from hypersplenism and marrow involvement.
  phenotype_term:
    preferred_term: Thrombocytopenia
    term:
      id: HP:0001873
      label: Thrombocytopenia
  evidence:
  - reference: PMID:35456468
    reference_title: "Phenotype Expansion for Atypical Gaucher Disease Due to Homozygous Missense PSAP Variant in a Large Consanguineous Pakistani Family."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "hepatosplenomegaly, kyphosis, and thrombocytopenia"
    explanation: "Thrombocytopenia is part of the atypical Gaucher phenotype."
inheritance:
- name: Autosomal recessive
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  evidence:
  - reference: PMID:35456468
    reference_title: "Phenotype Expansion for Atypical Gaucher Disease Due to Homozygous Missense PSAP Variant in a Large Consanguineous Pakistani Family."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A homozygous missense variant c.1076A>C: p.(Glu359Ala) in exon 10 of the PSAP"
    explanation: "A homozygous PSAP variant in affected siblings indicates autosomal recessive inheritance."
genetic:
- name: PSAP
  association: Biallelic PSAP variants abolishing saposin C
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  gene_term:
    preferred_term: PSAP
    term:
      id: hgnc:9498
      label: PSAP
  evidence:
  - reference: PMID:35456468
    reference_title: "Phenotype Expansion for Atypical Gaucher Disease Due to Homozygous Missense PSAP Variant in a Large Consanguineous Pakistani Family."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Atypical Gaucher disease is caused by variants in the PSAP gene."
    explanation: "PSAP variants cause atypical (saposin C deficiency) Gaucher disease."
diagnosis:
- name: Glucocerebrosidase assay with PSAP sequencing
  diagnosis_term:
    preferred_term: clinical laboratory procedure
    term:
      id: MAXO:0000006
      label: clinical laboratory procedure
  description: >-
    A Gaucher-like phenotype with normal glucocerebrosidase (beta-glucosidase) activity is
    the key clue; diagnosis is confirmed by PSAP sequencing.
  markers: Normal beta-glucosidase activity with a Gaucher-like phenotype and elevated glucosylceramide.
  evidence:
  - reference: PMID:17919309
    reference_title: "Non-neuronopathic Gaucher disease due to saposin C deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Saposin (SAP-) C is required for glucosylceramide degradation, and its deficiency results in a variant form of Gaucher disease."
    explanation: "The variant Gaucher phenotype with normal enzyme prompts PSAP/saposin C testing."
- name: PSAP molecular genetic testing
  diagnosis_term:
    preferred_term: genetic testing
    term:
      id: MAXO:0000127
      label: genetic testing
  description: Confirmatory biallelic PSAP sequencing.
  evidence:
  - reference: PMID:35456468
    reference_title: "Phenotype Expansion for Atypical Gaucher Disease Due to Homozygous Missense PSAP Variant in a Large Consanguineous Pakistani Family."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The family was investigated using exome and Sanger sequencing."
    explanation: "Molecular sequencing of PSAP confirms the diagnosis."
differential_diagnoses:
- name: Gaucher disease
  description: >-
    Classic Gaucher disease caused by glucocerebrosidase (GBA1) deficiency, with the same
    glucosylceramide storage but a deficient enzyme.
  disease_term:
    preferred_term: Gaucher disease
    term:
      id: MONDO:0018150
      label: Gaucher disease
  distinguishing_features:
  - Caused by deficient glucocerebrosidase enzyme activity (GBA1), whereas saposin C deficiency leaves enzyme activity normal.
  evidence:
  - reference: PMID:38928321
    reference_title: "Deficiency of Glucocerebrosidase Activity beyond Gaucher Disease: PSAP and LIMP-2 Dysfunctions."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "GCase deficiency causes Gaucher Disease (GD), which is mainly due to biallelic pathogenetic variants in the GCase-encoding gene, GBA1."
    explanation: "Classic Gaucher disease is GBA1 enzyme deficiency, distinct from the saposin C cofactor defect."
treatments:
- name: Supportive Care
  description: >-
    No saposin-C-specific disease-modifying therapy is established; management is
    supportive and symptomatic, drawing on approaches used for classic Gaucher disease.
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
definitions:
- name: Clinical case definition of saposin C deficiency Gaucher disease
  definition_type: CASE_DEFINITION
  description: >-
    Gaucher disease due to saposin C deficiency is an atypical Gaucher disease defined by
    biallelic PSAP variants abolishing the saposin C activator, with glucosylceramide
    accumulation and a Gaucher-like phenotype despite normal glucocerebrosidase enzyme
    activity.
  scope: Disease-level case definition for saposin C deficiency Gaucher disease.
  evidence:
  - reference: PMID:17919309
    reference_title: "Non-neuronopathic Gaucher disease due to saposin C deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Saposin (SAP-) C is required for glucosylceramide degradation, and its deficiency results in a variant form of Gaucher disease."
    explanation: "Anchors the case definition in saposin C deficiency causing variant Gaucher disease."
📚

References & Deep Research

Deep Research

1
Falcon
Gaucher Disease Due to Saposin C Deficiency (PSAP/SapC): Comprehensive Disease Characteristics Report
Edison Scientific Literature 26 citations 2026-06-13T14:24:05.777258

Gaucher Disease Due to Saposin C Deficiency (PSAP/SapC): Comprehensive Disease Characteristics Report

Target disease

  • Disease name: Gaucher disease due to saposin C deficiency (PSAP-related “atypical Gaucher disease”) (tamargo2012theroleof pages 1-2, motta2014gaucherdiseasedue pages 1-2)
  • Category: Mendelian / lysosomal storage disease (autosomal recessive) (tamargo2012theroleof pages 1-2, motta2014gaucherdiseasedue pages 1-2)
  • MONDO ID: Not identified in the retrieved full-text evidence set (tamargo2012theroleof pages 1-2, motta2014gaucherdiseasedue pages 1-2)

1. Disease Information

1.1 Concise overview (current understanding)

Gaucher disease due to saposin C deficiency is an ultra-rare lysosomal disorder in which biallelic pathogenic variants in PSAP (prosaposin) impair production/function of saposin C (SapC), an essential activator/cofactor for lysosomal glucocerebrosidase (GCase). This causes a Gaucher-like phenotype via impaired degradation of glucosylceramide (GlcCer) and related sphingolipids, and can clinically resemble non-neuronopathic (type 1-like) or neuronopathic (type 3-like) Gaucher disease—sometimes despite normal in vitro GCase activity assays (tamargo2012theroleof pages 1-2, rafi1993mutationalanalysisin pages 1-3, motta2014gaucherdiseasedue pages 1-2).

1.2 Key identifiers (as evidenced in retrieved literature)

Disease/Concept Identifier type Identifier/value Notes (inheritance, subtype, comments) Source
Gaucher disease due to saposin C deficiency MIM/OMIM disease ID 610539 Rare PSAP-related Gaucher-like disorder; autosomal recessive; can phenocopy type 1 or type 3 Gaucher disease; standard Orphanet/MONDO/MeSH/ICD identifiers were not found in the evidence (liaqat2022phenotypeexpansionfor pages 1-2, tamargo2012theroleof pages 1-2) Genes 2022; Mol Genet Metab 2012
Variant Gaucher disease due to saposin C deficiency Synonym variant Gaucher disease due to saposin C deficiency Historical/alternative phrasing for PSAP saposin C deficiency causing Gaucher-like disease (rafi1993mutationalanalysisin pages 1-3, motta2014gaucherdiseasedue pages 1-2) Somatic Cell Mol Genet 1993; Hum Mol Genet 2014
Atypical Gaucher disease due to PSAP Synonym atypical Gaucher disease due to PSAP Used for PSAP-associated Gaucher spectrum with phenotypic heterogeneity, including visceral and neurologic manifestations (liaqat2022phenotypeexpansionfor pages 5-7, liaqat2022phenotypeexpansionfor pages 1-2) Genes 2022
PSAP gene MIM/OMIM gene ID 176801 Encodes prosaposin, precursor of saposins A-D; biallelic pathogenic variants can cause saposin C deficiency or broader prosaposin deficiency (liaqat2022phenotypeexpansionfor pages 1-2, motta2014gaucherdiseasedue pages 1-2) Genes 2022; Hum Mol Genet 2014
GBA gene MIM/OMIM gene ID 606463 Encodes glucocerebrosidase/GCase; canonical Gaucher disease gene; SapC is its essential activator/cofactor (liaqat2022phenotypeexpansionfor pages 1-2, tamargo2012theroleof pages 1-2, motta2014gaucherdiseasedue pages 1-2) Genes 2022; Mol Genet Metab 2012; Hum Mol Genet 2014
Gaucher disease type 1 MIM/OMIM disease ID 230800 Non-neuronopathic Gaucher reference subtype; SapC deficiency may clinically resemble type 1 in some patients (tamargo2012theroleof pages 1-2, motta2014gaucherdiseasedue pages 1-2) Mol Genet Metab 2012; Hum Mol Genet 2014
Gaucher disease type 2 MIM/OMIM disease ID 230900 Acute neuronopathic Gaucher reference subtype; cited in review context for GD classification (pavan2024deficiencyofglucocerebrosidase pages 2-4) Int J Mol Sci 2024
Gaucher disease type 3 MIM/OMIM disease ID 231000 Chronic neuronopathic Gaucher reference subtype; SapC deficiency often discussed as type 3-like/neuronopathic (tamargo2012theroleof pages 1-2, pavan2024deficiencyofglucocerebrosidase pages 2-4) Mol Genet Metab 2012; Int J Mol Sci 2024
Prosaposin deficiency MIM/OMIM disease ID 611721 Distinct from isolated SapC deficiency; complete prosaposin deficiency affects all saposins and is typically more severe (tamargo2012theroleof pages 1-2, pavan2024deficiencyofglucocerebrosidase pages 1-2) Mol Genet Metab 2012; Int J Mol Sci 2024
Saposin C Molecular concept Essential activator of GCase Derived from prosaposin; promotes GCase interaction with anionic lysosomal membranes and stabilizes enzyme activity/protein; deficiency can present despite normal in vitro GCase activity in some assays (tamargo2012theroleof pages 1-2, tamargo2012theroleof pages 5-7, motta2014gaucherdiseasedue pages 1-2) Mol Genet Metab 2012; Hum Mol Genet 2014
Evidence base Resource provenance Aggregated disease literature plus individual case reports Knowledge derives mainly from case reports/small families and mechanistic studies, not EHR-scale datasets; only a handful of patients have been reported worldwide (liaqat2022phenotypeexpansionfor pages 5-7, tamargo2012theroleof pages 5-7) Genes 2022; Mol Genet Metab 2012
External identifiers not found in retrieved evidence Identifier status Orphanet/MONDO/MeSH/ICD not found Absence here reflects retrieved evidence only and should not be interpreted as proof that no such identifiers exist in external databases (liaqat2022phenotypeexpansionfor pages 1-2, tamargo2012theroleof pages 1-2, motta2014gaucherdiseasedue pages 1-2) Genes 2022; Mol Genet Metab 2012; Hum Mol Genet 2014

Table: This table summarizes the key disease and gene identifiers, core synonyms, and classification facts for Gaucher disease due to saposin C deficiency. It is useful for normalizing nomenclature and linking PSAP-related disease concepts to canonical Gaucher disease subtypes.

Notes on identifiers: Orphanet, MeSH, ICD-10/ICD-11, and MONDO identifiers were not present in the retrieved documents and therefore cannot be reliably populated from this evidence set (tamargo2012theroleof pages 1-2, motta2014gaucherdiseasedue pages 1-2).

1.3 Synonyms / alternative names

  • Gaucher disease due to saposin C deficiency (tamargo2012theroleof pages 1-2, motta2014gaucherdiseasedue pages 1-2)
  • Variant Gaucher disease caused by SAP-2 / saposin C (historical terminology) (rafi1993mutationalanalysisin pages 1-3)
  • Atypical Gaucher disease due to PSAP (liaqat2022phenotypeexpansionfor pages 5-7, liaqat2022phenotypeexpansionfor pages 1-2)

1.4 Evidence provenance

The evidence base is dominated by single-patient case reports and small families, plus mechanistic in vitro and animal-model studies; it is not derived from EHR-scale aggregated cohorts (tamargo2012theroleof pages 5-7, liaqat2022phenotypeexpansionfor pages 5-7).


2. Etiology

2.1 Primary causal factors

  • Genetic cause: biallelic pathogenic variants in PSAP affecting the SapC domain (autosomal recessive) (tamargo2012theroleof pages 1-2, motta2014gaucherdiseasedue pages 1-2).
  • Mechanistic cause: loss of functional SapC reduces/impairs membrane-associated GCase activity and/or stability, leading to lysosomal glycosphingolipid storage (GlcCer ± GlcSph and other sphingolipids) and downstream macrophage and/or CNS pathology (tamargo2012theroleof pages 4-5, motta2014gaucherdiseasedue pages 1-2, pavan2024deficiencyofglucocerebrosidase pages 9-10).

2.2 Risk factors

  • Genetic: consanguinity increases risk by increasing probability of homozygous PSAP variants; a large consanguineous Pakistani family with multiple affected individuals has been reported (liaqat2022phenotypeexpansionfor pages 5-7).
  • Environmental / infectious: no disease-specific environmental or infectious risk factors were identified in the retrieved evidence.

2.3 Protective factors

No protective genetic or environmental factors were reported in the retrieved evidence.

2.4 Gene–environment interactions

No PSAP SapC-deficiency-specific gene–environment interaction evidence was found in the retrieved documents.


3. Phenotypes (clinical features) and ontology mapping

3.1 Phenotype spectrum and clinical heterogeneity

Across the limited number of reported patients, SapC deficiency can produce type 1-like (visceral/hematologic/bone) disease and/or type 3-like neuronopathic disease. A review of six reported patients described presentations ranging from type 1-like to type 3-like, including adult siblings with mild neurologic deterioration (tamargo2012theroleof pages 5-7, tamargo2012theroleof pages 1-2).

3.2 Structured phenotype + diagnostic feature table (with HPO suggestions)

Phenotype/feature HPO term suggestion Typical onset/course Notes/frequency (if available) Key evidence
Hepatosplenomegaly HP:0001433 Hepatosplenomegaly Infantile to childhood; progressive or persistent Commonly reported visceral feature across cases/families Seen in classic case summaries and recent reports; 4-month-old PSAP case had hepatosplenomegaly; also reported in Pakistani family and Indian infant (tamargo2012theroleof pages 1-2, pavan2024deficiencyofglucocerebrosidase pages 2-4, liaqat2022phenotypeexpansionfor pages 5-7, li2025prosaposinamultifaceted pages 10-11)
Anemia HP:0001903 Anemia Infantile/childhood; chronic Reported in Gaucher-like visceral presentations; not quantified for all cases Listed among typical GD-like findings in SapC deficiency; present in Indian/Chinese summaries (tamargo2012theroleof pages 1-2, li2025prosaposinamultifaceted pages 10-11)
Thrombocytopenia HP:0001873 Thrombocytopenia Infantile to childhood; chronic Recurrent hematologic finding Reported in Pakistani family and in general SapC-deficiency phenotype descriptions (tamargo2012theroleof pages 1-2, liaqat2022phenotypeexpansionfor pages 5-7, li2025prosaposinamultifaceted pages 10-11)
Bone lesions / kyphosis HP:0002650 Scoliosis/Kyphosis; HP:0002758 Osteolysis or HP:0000930 Generalized osteopenia Childhood to adult; progressive/variable Bone lesions are part of GD-like spectrum; kyphosis specifically reported in Pakistani family Bone disease noted in reviews; kyphosis reported with p.Glu359Ala family (tamargo2012theroleof pages 1-2, liaqat2022phenotypeexpansionfor pages 5-7)
Pulmonary hypertension HP:0002092 Pulmonary hypertension Variable; likely later complication Mentioned as part of GD clinical spectrum in SapC-deficiency review, not clearly frequency-defined for SapC cases Listed among clinical features in 2014 mechanistic paper introduction (motta2014gaucherdiseasedue pages 1-2)
Seizures / encephalopathy HP:0001250 Seizure; HP:0001298 Encephalopathy Early infantile in severe neuronopathic cases; can be rapidly progressive Indian infant had encephalopathy and refractory seizures; severe neonatal/infantile presentations reported 2-month-old infant with encephalopathy and resistant tonic-clonic seizures died by 4 months (li2025prosaposinamultifaceted pages 10-11)
Hypotonia HP:0001252 Hypotonia Early infantile; progressive in severe cases Present in severe infantile case; also 4-month-old PSAP_PT had hypotonia Reported in Indian infant and PSAP_PT with severe neurologic disease (li2025prosaposinamultifaceted pages 10-11, pavan2024deficiencyofglucocerebrosidase pages 2-4)
Nystagmus HP:0000639 Nystagmus Early infantile in severe neuronopathic case Reported in PSAP_PT suspected as GD2-like 4-month-old infant had hypotonia, nystagmus, swallowing difficulty (pavan2024deficiencyofglucocerebrosidase pages 2-4)
Ataxia HP:0001251 Ataxia Childhood to adult; progressive neurologic course Seen in type 3-like / neuronopathic presentations and mouse models Included in human clinical spectrum and supported by SapC-deficient mouse phenotype (tamargo2012theroleof pages 1-2, sun2010specificsaposinc pages 1-2)
Myoclonic epilepsy HP:0001336 Myoclonic seizures Childhood/adolescent; progressive neuronopathic course Reported in GD-like neurologic spectrum due to SapC deficiency Included in SapC-deficiency clinical overlap with type 3 GD (tamargo2012theroleof pages 1-2)
Abnormal horizontal saccades HP:0000640 Oculomotor apraxia / HP:0000616 Abnormality of eye movement Childhood/adolescent; neurologic Characteristic neuronopathic GD-like feature in some reported cases Listed in review of six reported patients (tamargo2012theroleof pages 1-2)
Hearing impairment HP:0000365 Hearing impairment Congenital/prelingual or childhood; non-progressive/progressive uncertain All affected members in Pakistani family had hearing impairment; prelingual profound SNHL highlighted Strong feature in p.Glu359Ala family (liaqat2022phenotypeexpansionfor pages 5-7)
Vestibular dysfunction HP:0001751 Vestibular areflexia / HP:0001756 Vestibular dysfunction Childhood; chronic Reported with hearing impairment in Pakistani family Present in all affected family members in phenotype-expansion report (liaqat2022phenotypeexpansionfor pages 5-7)
GCase activity may be normal in vitro HP:0012378 Abnormal enzyme/coenzyme activity Diagnostic caveat; may obscure diagnosis Important distinguishing feature: SapC deficiency can present despite normal standard GCase assay results Human SapC-deficient cases can show normal in vitro GCase activity; one case had normal skin fibroblast GCase despite biomarker abnormalities (tamargo2012theroleof pages 1-2, rafi1993mutationalanalysisin pages 1-3, li2025prosaposinamultifaceted pages 11-13)
Tissue glucosylceramide accumulation HP:0011015 Abnormal sphingolipid concentration Persistent biochemical hallmark May be demonstrated in spleen/tissue despite normal enzyme assay Spleen glucosylceramide accumulation documented in variant Gaucher due to SapC deficiency (rafi1993mutationalanalysisin pages 1-3)
Plasma chitotriosidase elevation HP:0034046 Increased circulating chitotriosidase level Elevated at diagnosis; reflects macrophage activation Markedly elevated in severe infantile PSAP case PSAP_PT chitotriosidase 2951.0 nmol/mL/h (pavan2024deficiencyofglucocerebrosidase pages 2-4)
Plasma glucosylsphingosine (GlcSph) elevation HP:0034383 Increased circulating glucosylsphingosine Elevated at diagnosis Useful GD biomarker in PSAP-related GCase deficiency PSAP_PT plasma GlcSph 19.0 ng/mL (pavan2024deficiencyofglucocerebrosidase pages 2-4)
Lyso-Gb3 elevation HP:0034380 Abnormal globotriaosylsphingosine level Elevated at diagnosis in reported case Ancillary lipid biomarker; may assist broader sphingolipid profiling PSAP_PT Lyso-Gb3 1.98 ng/mL (pavan2024deficiencyofglucocerebrosidase pages 2-4)
PPCS elevation HP:0034385 Abnormal lysosphingolipid profile Elevated at diagnosis in reported case Additional plasma biomarker reported in 2024 study PSAP_PT PPCS 745.9 ng/mL (pavan2024deficiencyofglucocerebrosidase pages 2-4)
Genetic testing for PSAP variants HP:0000007 Autosomal recessive inheritance Confirmatory test; indicated when GD suspected but GBA1 negative or biochemistry atypical Reported pathogenic variant classes include missense, nonsense, splice-site, start-loss, and deletions PSAP sequencing/WES/Sanger used across cases; variants include p.E297*, p.Glu359Ala, p.C382G/F, p.L349P, c.1005+1G>A (liaqat2022phenotypeexpansionfor pages 5-7, motta2014gaucherdiseasedue pages 1-2, pavan2024deficiencyofglucocerebrosidase pages 2-4)
Negative GBA1 testing should trigger PSAP evaluation HP:0000007 Autosomal recessive inheritance Diagnostic workflow recommendation Particularly important in infantile GD-like disease with elevated biomarkers and low-normal/normal GCase assays 2024 PSAP_PT was GBA1-negative then diagnosed by PSAP testing; Indian report explicitly advises considering specific activator deficiency when GD is suspected with partially deficient or near-normal GBA activity (pavan2024deficiencyofglucocerebrosidase pages 2-4, li2025prosaposinamultifaceted pages 10-11)

Table: This table summarizes the reported clinical spectrum and key diagnostic findings for Gaucher disease due to saposin C deficiency caused by PSAP variants. It is useful for distinguishing this ultra-rare activator deficiency from canonical GBA1-related Gaucher disease, especially when enzyme activity is normal or only mildly reduced.

3.3 Quality of life impact

Formal QoL instruments (e.g., EQ-5D/SF-36/PROMIS) were not reported in the retrieved evidence. Severe infantile neuronopathic disease is expected to substantially impair functioning (hypotonia, swallowing difficulty, seizures), while chronic neurologic disease (ataxia) and visceral disease (organomegaly, cytopenias) can impair daily activity and endurance (pavan2024deficiencyofglucocerebrosidase pages 2-4, tamargo2012theroleof pages 1-2).


4. Genetic / Molecular Information

4.1 Causal gene(s)

  • PSAP (prosaposin; SapC derived from prosaposin proteolysis) (tamargo2012theroleof pages 1-2, motta2014gaucherdiseasedue pages 1-2).

4.2 Pathogenic variants (examples from primary/review literature)

Evidence-supported PSAP/SapC-domain pathogenic or likely pathogenic variants include: - c.1144T>G (p.Cys382Gly) reported in a variant Gaucher case with glucosylceramide accumulation despite normal measured glucocerebrosidase activity (rafi1993mutationalanalysisin pages 1-3). - SapC lesions summarized in mechanistic work: p.C315S, p.342_348FDKMCSKdel, p.L349P, p.C382G, p.C382F (motta2014gaucherdiseasedue pages 1-2). - A consanguineous family with likely pathogenic c.1076A>C (p.Glu359Ala) in the SapC domain; variant is rare in gnomAD and lies in the SapC GCase-binding region (aa 351–390) (liaqat2022phenotypeexpansionfor pages 5-7). - Severe infantile case: c.889G>T (p.E297*) with nonsense-mediated mRNA decay; GD2-like suspicion clinically (pavan2024deficiencyofglucocerebrosidase pages 2-4).

Variant classes observed: missense, in-frame deletion, nonsense, splice-site; many reported variants affect SapC cysteines/disulfide bonds or otherwise destabilize the SapC fold (tamargo2012theroleof pages 5-7, motta2014gaucherdiseasedue pages 1-2).

4.3 Functional consequences

  • SapC is a small, cysteine-rich activator/cofactor with disulfide bonds that confer acid stability; multiple disease mutants adopt aberrant disulfide arrangements and are rapidly degraded, with evidence implicating autophagy-mediated degradation as a key pathogenic mechanism in SapC deficiency (motta2014gaucherdiseasedue pages 1-2).
  • SapC also protects GCase from proteolysis; absence of SapC can reduce tissue GCase activity and increase degradation, which can be modulated by protease inhibitors in experimental systems (tamargo2012theroleof pages 4-5).

4.4 Modifier genes / epigenetics / chromosomal abnormalities

No SapC-deficiency-specific modifier gene, epigenetic, or chromosomal abnormality evidence was found in the retrieved documents.


5. Environmental Information

No disease-specific environmental, lifestyle, or infectious contributors were identified in the retrieved evidence; the disorder is primarily genetic (tamargo2012theroleof pages 1-2, motta2014gaucherdiseasedue pages 1-2).


6. Mechanism / Pathophysiology

6.1 Causal chain (trigger → molecular defect → cellular dysfunction → clinical phenotype)

  1. Upstream trigger: biallelic PSAP variants reduce/abolish functional SapC production or stability (including nonsense-mediated decay for truncating variants) (pavan2024deficiencyofglucocerebrosidase pages 2-4, pavan2024deficiencyofglucocerebrosidase pages 9-10).
  2. Primary molecular defect: SapC normally binds anionic lysosomal membranes and GCase, enabling membrane-associated presentation/access of GlcCer to the enzyme; SapC also stabilizes/protects GCase from proteolysis (tamargo2012theroleof pages 4-5, tamargo2012theroleof pages 5-7).
  3. Biochemical consequence: reduced effective GCase-mediated degradation causes storage of GlcCer and often glucosylsphingosine (GlcSph) (and sometimes other sphingolipids) (tamargo2012theroleof pages 5-7, pavan2024deficiencyofglucocerebrosidase pages 9-10).
  4. Cellular pathology: lipid-laden macrophages (“Gaucher cells”) drive inflammation and visceral disease; in neuronopathic cases, CNS pathology includes neuronal inclusions, Purkinje cell loss, axonal degeneration, and glial activation/inflammation (sun2010specificsaposinc pages 1-2, tamargo2012theroleof pages 5-7).
  5. Clinical manifestations: hepatosplenomegaly, cytopenias, bone disease; and/or neurologic impairment (hypotonia, seizures, ataxia, abnormal eye movements, etc.) (tamargo2012theroleof pages 1-2, pavan2024deficiencyofglucocerebrosidase pages 2-4).

6.2 Pathways, processes, and suggested GO terms

Key molecular/cellular processes (GO Biological Process suggestions): - Lysosomal glycosphingolipid catabolic process / sphingolipid metabolic process (supported conceptually by impaired GlcCer breakdown) (pavan2024deficiencyofglucocerebrosidase pages 1-2, pavan2024deficiencyofglucocerebrosidase pages 9-10) - Lysosome organization and membrane-associated catabolism (SapC-mediated membrane interaction/liftase model) (tamargo2012theroleof pages 4-5) - Autophagy (as a degradation route for mutant SapC proteins) (motta2014gaucherdiseasedue pages 1-2) - Neuroinflammatory response / glial activation (microglia, astrocytes activated in SapC-deficient mouse CNS) (sun2010specificsaposinc pages 1-2)

6.3 Cell types and suggested CL terms

Cell Ontology (CL) suggestions based on evidence: - Macrophage (Gaucher cells; mononuclear phagocyte system involvement) (tamargo2012theroleof pages 1-2, motta2014gaucherdiseasedue pages 1-2) - Microglial cell (activated microglia in SapC-deficient mouse CNS) (sun2010specificsaposinc pages 1-2) - Astrocyte (astrocyte activation in SapC-deficient mouse CNS) (sun2010specificsaposinc pages 1-2) - Purkinje cell (cerebellar Purkinje neuron loss in SapC-deficient mouse model) (sun2010specificsaposinc pages 1-2)

6.4 Expert mechanistic analysis (authoritative synthesis)

High-citation expert reviews emphasize that SapC functions as a membrane-active cofactor enabling optimal GCase function and that SapC deficiency can yield a Gaucher phenotype even with apparently normal in vitro enzyme assays, which has important diagnostic implications (tamargo2012theroleof pages 1-2, tamargo2012theroleof pages 4-5).

Direct abstract quote (animal model; mechanistic): - Sun et al. report: “The few patients with saposin C deficiency develop a Gaucher disease-like central nervous system (CNS) phenotype attributed to diminished glucosylceramide (GC) cleavage activity by acid β-glucosidase (GCase).” (Human Molecular Genetics; Dec 2010; https://doi.org/10.1093/hmg/ddp531) (sun2010specificsaposinc pages 1-2)


7. Anatomical Structures Affected

7.1 Organ/system level (UBERON suggestions)

  • Liver / spleen (hepatosplenomegaly): mononuclear phagocyte system storage involvement (UBERON: liver; UBERON: spleen) (tamargo2012theroleof pages 1-2, pavan2024deficiencyofglucocerebrosidase pages 2-4).
  • Bone / skeletal system: bone lesions and kyphosis reported; osteoarticular involvement is typical of Gaucher-like disease (UBERON: bone of lower limb / vertebral column) (tamargo2012theroleof pages 1-2, liaqat2022phenotypeexpansionfor pages 5-7).
  • Central nervous system: neuronopathic presentations include seizures, hypotonia, ataxia, eye movement abnormalities; SapC-deficient mice show cerebellar and axonal pathology (UBERON: brain; UBERON: cerebellum; UBERON: spinal cord) (sun2010specificsaposinc pages 1-2, pavan2024deficiencyofglucocerebrosidase pages 2-4).

7.2 Tissue/cell level

  • Monocyte/macrophage lineage cells with lysosomal lipid storage (motta2014gaucherdiseasedue pages 1-2).
  • Cerebellar neuronal populations (Purkinje cells) and glial cells (microglia, astrocytes) in neurologic disease models (sun2010specificsaposinc pages 1-2).

7.3 Subcellular level (GO Cellular Component suggestions)

  • Lysosome (site of glycosphingolipid catabolism and SapC–GCase function) (pavan2024deficiencyofglucocerebrosidase pages 1-2, tamargo2012theroleof pages 4-5).

8. Temporal Development

8.1 Onset

Onset is variable, ranging from infantile severe neurologic disease (including GD2-like presentations) to childhood/adult-onset neurologic deterioration or more type 1-like disease without clear CNS signs in some families (pavan2024deficiencyofglucocerebrosidase pages 2-4, tamargo2012theroleof pages 5-7, liaqat2022phenotypeexpansionfor pages 5-7).

8.2 Progression

Severe infantile cases may progress rapidly and can be fatal within months (pavan2024deficiencyofglucocerebrosidase pages 2-4). Other cases show chronic neurologic progression (e.g., ataxia) or chronic visceral disease (tamargo2012theroleof pages 5-7, tamargo2012theroleof pages 1-2).


9. Inheritance and Population

9.1 Inheritance

Autosomal recessive inheritance is strongly supported by multiple reports of homozygous/biallelic PSAP variants and occurrence in consanguineous families (tamargo2012theroleof pages 1-2, liaqat2022phenotypeexpansionfor pages 5-7, pavan2024deficiencyofglucocerebrosidase pages 2-4).

9.2 Epidemiology

No population-level prevalence or incidence estimates were identified in the retrieved literature. Available synthesis notes only a handful of published patients worldwide (e.g., six described in one review; and ~seven reported cases cited in a later family report), consistent with an ultra-rare condition (tamargo2012theroleof pages 5-7, liaqat2022phenotypeexpansionfor pages 5-7).

9.3 Population genetics / allele frequency example

The likely pathogenic PSAP c.1076A>C (p.Glu359Ala) variant was reported as rare in gnomAD (overall AF 5.3×10−5; South Asian AF 3.6×10−4; no homozygotes in gnomAD per authors) (liaqat2022phenotypeexpansionfor pages 5-7).


10. Diagnostics

10.1 Clinical suspicion

Consider PSAP/SapC deficiency when a patient has a Gaucher-like phenotype (hepatosplenomegaly, cytopenias ± bone disease and/or neurologic disease) but: - GBA1 testing is negative, and/or - GCase activity is normal/low-normal on standard assays (diagnostic pitfall), and/or - biomarkers suggest Gaucher-like macrophage activation and glycosphingolipid storage (pavan2024deficiencyofglucocerebrosidase pages 2-4, rafi1993mutationalanalysisin pages 1-3, tamargo2012theroleof pages 1-2).

10.2 Laboratory biomarkers and statistics from recent study (2024)

A 2024 biochemical profiling study reports markedly elevated Gaucher biomarkers in a PSAP case (PSAP_PT): - Chitotriosidase: 2951.0 nmol/mL/h - Plasma glucosylsphingosine (GlcSph): 19.0 ng/mL - Lyso-Gb3: 1.98 ng/mL - PPCS: 745.9 ng/mL with a homozygous truncating PSAP variant (c.889G>T; p.E297*) and severe infantile disease (Jun 2024; https://doi.org/10.3390/ijms25126615) (pavan2024deficiencyofglucocerebrosidase pages 2-4).

10.3 Enzyme activity testing caveat

A seminal primary report documented glucosylceramide accumulation in spleen despite normal measured glucocerebrosidase activity, supporting “activator deficiency” rather than enzyme deficiency (rafi1993mutationalanalysisin pages 1-3).

10.4 Genetic testing approach

  • Confirmatory testing is PSAP sequencing (single-gene, lysosomal storage disease panels, or exome/genome sequencing) and variant interpretation in the context of phenotype and biochemical findings (liaqat2022phenotypeexpansionfor pages 5-7, pavan2024deficiencyofglucocerebrosidase pages 2-4).

11. Outcome / Prognosis

Prognosis appears highly variable and genotype/phenotype dependent. A severe infantile PSAP truncating-variant case with GD2-like features died a few months after diagnosis (pavan2024deficiencyofglucocerebrosidase pages 2-4). Milder phenotypes without overt CNS involvement have been reported in families, implying potentially longer survival (liaqat2022phenotypeexpansionfor pages 5-7). Systematic survival statistics are not available in the retrieved evidence.


12. Treatment

12.1 Disease-directed therapies

No controlled clinical trial evidence specific to SapC deficiency treatment was identified in the retrieved documents, and the clinical trials search did not return SapC-deficiency-specific interventional trials.

Mechanistically, SapC deficiency is an activator/cofactor deficiency rather than a primary GCase catalytic deficiency. Expert reviews discuss that increasing SapC levels or restoring SapC–GCase interactions could be therapeutic in principle, and that chemical chaperones can improve folding/trafficking and SapC–enzyme interactions in experimental contexts, but these are not presented as established clinical therapies for SapC deficiency in the retrieved evidence (tamargo2012theroleof pages 5-7, tamargo2012theroleof pages 7-8).

12.2 Supportive care

Supportive management is implied by clinical features (e.g., management of cytopenias, organomegaly complications, seizures, swallowing dysfunction), but specific guidelines were not found in the retrieved evidence.

12.3 MAXO term suggestions

  • Enzyme activity assay / enzyme replacement-related actions are not directly evidenced as effective here; nevertheless, for knowledge-base normalization:
  • MAXO: enzyme replacement therapy (as a general Gaucher therapy class; disease-specific effectiveness for SapC deficiency not evidenced)
  • MAXO: anticonvulsant therapy (for seizure management in neuronopathic presentations)
  • MAXO: supportive respiratory care / feeding support (for severe infantile neurologic disease)

13. Prevention

13.1 Primary/secondary prevention (genetic)

Given autosomal recessive inheritance, prevention is primarily through genetic counseling and prenatal or preimplantation genetic testing in families with known PSAP variants. A PSAP-related infantile case report summary indicates prenatal diagnosis in a subsequent pregnancy identified a carrier fetus who was unaffected postnatally (reported as part of the PSAP infantile case summary in a synthesis) (li2025prosaposinamultifaceted pages 10-11).


14. Other Species / Natural Disease

Natural SapC-deficiency animal disease was not identified in the retrieved evidence.


15. Model Organisms

15.1 Mouse models

A selective SapC-deficient mouse model (knock-in point mutation eliminating SapC) exhibits a CNS-predominant phenotype (hindlimb weakness, progressive ataxia, neurophysiologic impairment, dorsal root ganglion storage cells, Purkinje cell loss, glial activation) with little/no visceral organ storage—highlighting both mechanistic insight and limitations in recapitulating human visceral disease (sun2010specificsaposinc pages 1-2).

Direct abstract quote (mouse model): - “By 1 year, the C−/− mice exhibited weakness of the hind limbs and progressive ataxia.” (Human Molecular Genetics; Dec 2010; https://doi.org/10.1093/hmg/ddp531) (sun2010specificsaposinc pages 1-2)


2023–2024 developments and real-world implementation highlights

  1. 2024 biochemical profiling beyond GBA1 Gaucher disease: A 2024 study explicitly compares GCase-deficiency etiologies (GBA1 vs PSAP vs SCARB2/LIMP-2) and provides quantified biomarker data (chitotriosidase, GlcSph, Lyso-Gb3, PPCS) in a PSAP case, supporting real-world diagnostic workflows for “Gaucher-like” presentations with negative GBA1 testing (Jun 2024; https://doi.org/10.3390/ijms25126615) (pavan2024deficiencyofglucocerebrosidase pages 2-4, pavan2024deficiencyofglucocerebrosidase pages 1-2).
  2. 2023 case-based evidence of PSAP-related disease burden: A 2023 neonatal case report of combined saposin deficiency illustrates severe neurovisceral presentations and reinforces that enzymatic and genetic confirmation plus counseling are implemented in real clinical settings (Mar 2023; https://doi.org/10.1016/j.mjafi.2021.01.024) (bhat2023combinedsaposindeficiency pages 1-2).

Evidence gaps (important for knowledge base curation)

  • Orphanet/MONDO/MeSH/ICD identifiers were not extractable from the retrieved full text and should be populated via dedicated database lookup rather than inferred here (tamargo2012theroleof pages 1-2, motta2014gaucherdiseasedue pages 1-2).
  • Treatment efficacy evidence (ERT/SRT/gene therapy) specifically for SapC deficiency was not found in the retrieved documents; mechanistic speculation exists, but clinical outcome evidence is not available in this evidence set (tamargo2012theroleof pages 5-7).
  • Epidemiology (prevalence/incidence) is not available in the retrieved literature, beyond statements of extreme rarity and small numbers of published cases (tamargo2012theroleof pages 5-7, liaqat2022phenotypeexpansionfor pages 5-7).

References

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