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IEMbase 0245: HGSNAT-related Heparan-alpha-glucosaminide N-acetyltransferase deficiency

Scope

Field Value
IEMbase ID 245
Nosology 20.2.05.01
Gene HGSNAT
External IDs OMIM:252930; ORPHA:79271
Generated mapping MAPPED; Sanfilippo_syndrome.yaml#MPS IIIC
Candidate DisMech targets Sanfilippo_syndrome.yaml#MPS IIIC
Review date 2026-07-07

IEMbase phenotype signal

IEMbase represents this as HGSNAT-related heparan-alpha-glucosaminide N-acetyltransferase deficiency, with alternate labels Sanfilippo syndrome type C severe, retinitis pigmentosa type 73 milder, mucopolysaccharidosis type 3C, and MPS IIIC. The record is autosomal recessive and treatability is marked yes, with no treatment rows in the cached JSON.

Biochemical rows include decreased acetyl-CoA:alpha-N-glucosaminide- N-acetyltransferase activity in white blood cells and increased urinary heparan sulfate and total glycosaminoglycans. Clinical rows include Alder-Reilly anomaly, diarrhea, dysostosis multiplex, hearing loss, and sleep disturbances. Characteristic rows include aggressive behavior, coarse facial features, hyperactivity, intellectual disability, liver dysfunction, neurologic regression, pigmentary retinopathy, seizures, and swallowing difficulties.

DisMech phenotype coverage

Sanfilippo_syndrome.yaml#MPS IIIC is the correct local target. The local file has subtype coverage for HGSNAT-related Sanfilippo syndrome type C/heparan- alpha-glucosaminide N-acetyltransferase deficiency, and the shared Sanfilippo entry covers autosomal recessive inheritance, heparan sulfate catabolic failure, heparan sulfate storage, progressive neurodegeneration, developmental regression, intellectual disability, behavioral problems, hyperactivity, sleep disturbance, seizures, swallowing and feeding difficulty, hearing and visual impairment, and mild systemic MPS features.

Concordance and completeness

Judgement: correct subtype-level mapping with high concordance.

IEMbase and DisMech agree on HGSNAT/MPS IIIC identity, heparan sulfate storage, total GAG elevation, neurobehavioral disease, seizures, sleep disturbance, swallowing difficulty, hearing involvement, and systemic MPS features. IEMbase adds useful specificity for the enzyme assay, pigmentary retinopathy, and the retinitis pigmentosa type 73/attenuated retina-focused label. The current local Sanfilippo file does not split that milder RP73 context into a separate disease target.

Curation actions

  • Keep this record mapped to Sanfilippo_syndrome.yaml#MPS IIIC.
  • Preserve the note that IEMbase spans severe Sanfilippo C and milder RP73 labeling.
  • Consider retinal phenotype detail if HGSNAT/MPS IIIC subtype coverage is refreshed.