IEMbase 0294: PSAP-related Gaucher disease-like disorder due to saposin C deficiency
Scope
| Field | Value |
|---|---|
| IEMbase ID | 294 |
| Nosology | 20.1.02.01 |
| Gene | PSAP |
| External IDs | OMIM:610539; ORPHA:309263 |
| Generated mapping | MAPPED; Gaucher_Disease_Due_To_Saposin_C_Deficiency.yaml |
| Candidate DisMech targets | Gaucher_Disease_Due_To_Saposin_C_Deficiency.yaml |
| Review date | 2026-07-07 |
IEMbase phenotype signal
IEMbase represents isolated saposin C deficiency, a PSAP cofactor disorder with a Gaucher-like presentation. Inheritance is autosomal recessive and treatability is unknown.
Clinical rows include anemia, abnormal eye movements, foam cells, hepatosplenomegaly, pathological fractures, myoclonic seizures, thrombocytopenia, bone pain, and developmental delay. Biochemical rows are particularly useful: markedly increased plasma chitotriosidase, normal beta-D-glucosidase activity, and increased serum glucosylsphingosine.
DisMech phenotype coverage
Gaucher_Disease_Due_To_Saposin_C_Deficiency.yaml is the correct local target.
The local entry explicitly models PSAP variants abolishing saposin C, impaired
glucocerebrosidase access to glucosylceramide despite normal GBA1 enzyme
activity, lysosomal glucosylceramide accumulation, Gaucher-like macrophage
storage, hepatosplenomegaly, and thrombocytopenia.
Local diagnosis also captures the main differentiator from classic Gaucher disease: a Gaucher-like phenotype with normal glucocerebrosidase activity and confirmatory PSAP sequencing.
Concordance and completeness
Judgement: correct high-concordance mapping to
Gaucher_Disease_Due_To_Saposin_C_Deficiency.yaml.
IEMbase and DisMech agree on PSAP/saposin C identity, recessive inheritance, Gaucher-like macrophage storage, hepatosplenomegaly, thrombocytopenia, normal glucocerebrosidase activity, and increased glucosylsphingosine. DisMech is stronger for the cofactor-defect mechanism and for distinguishing saposin C deficiency from GBA1 Gaucher disease.
IEMbase adds phenotype prompts that are not all explicit locally: anemia, abnormal eye movements, foam cells, pathological fractures, myoclonic seizures, bone pain, developmental delay, and chitotriosidase. These should be reviewed carefully because the local entry is intentionally conservative and the published case base is small.
Curation actions
- Keep this record mapped to
Gaucher_Disease_Due_To_Saposin_C_Deficiency.yaml. - Consider adding normal beta-D-glucosidase plus elevated glucosylsphingosine and chitotriosidase as biochemical prompts if supported by the local evidence base.
- Review IEMbase-only neurologic, ocular-motor, skeletal, hematologic, and foam cell rows before importing.