IEMbase 0032: GLDC-related nonketotic hyperglycinemia
Scope
| Field | Value |
|---|---|
| IEMbase ID | 32 |
| Nosology | 1.6.01.01 |
| Gene | GLDC |
| External IDs | OMIM:238300 |
| Generated mapping | MAPPED by alias_exact:glycine encephalopathy |
| Candidate DisMech targets | Nonketotic_Hyperglycinemia.yaml |
| Review date | 2026-07-07 |
IEMbase phenotype signal
IEMbase represents GLDC-related glycine cleavage system deficiency. The characteristic phenotype set includes seizures, hypotonia, burst-suppression EEG, hypsarrhythmia, multifocal epilepsy, corpus callosum agenesis or hypoplasia, and severe neonatal/infantile neurologic involvement.
Additional features include apnea, feeding difficulties, hiccups, lethargy, psychomotor delay, neurologic deterioration, drug-resistant epilepsy, hydrocephalus, posterior fossa anomalies, simplified gyral pattern, ataxia, chorea, spasticity, hyperactivity, optic atrophy, and elevated CSF glycine, plasma glycine, and CSF/plasma glycine ratio. Treatments listed are sodium benzoate and dextromethorphan/NMDA-antagonist therapy.
DisMech phenotype coverage
The generated mapping to Nonketotic_Hyperglycinemia.yaml is correct. DisMech
covers glycine cleavage system dysfunction, systemic and CNS glycine
accumulation, plasma and CSF glycine, CSF-to-plasma glycine ratio, seizures,
hypotonia, lethargy, apnea, global developmental delay, intellectual
disability, abnormal corpus callosum morphology, cerebral white-matter
abnormality, burst-suppression EEG, ADHD-like behavior, neonatal respiratory
distress, recurrent singultus, sodium benzoate, ketogenic diet, NMDA antagonist
therapy with caveats, anticonvulsant management, supportive care, and genetic
counseling.
Concordance and completeness
Judgement: correct mapping and high concordance. DisMech is strong mechanistically and therapeutically; IEMbase is richer for specific imaging and EEG subfeatures.
IEMbase adds hypsarrhythmia, multifocal epilepsy, drug-resistant epilepsy, feeding difficulties, hydrocephalus, posterior fossa anomalies, simplified gyral pattern, optic atrophy, chorea, spasticity, and explicit corpus-callosum agenesis/hypoplasia labels. DisMech adds D-serine and one-carbon metabolism context, glial-lineage developmental mechanisms, GCSH/lipoylation detail, ketogenic diet, anticonvulsant cautions, and broader supportive care.
Curation actions
- Keep the generated mapping.
- Consider adding selected EEG and MRI features from IEMbase, especially hypsarrhythmia, multifocal epilepsy, posterior fossa anomalies, hydrocephalus, and simplified gyral pattern.
- Consider adding feeding difficulty, drug-resistant epilepsy, optic atrophy, chorea, and spasticity if supported by NKH evidence.