Treatable Intellectual Disability

l.o. Non-Ketotic Hyperglycinemia

DIAGNOSIS

Gene
AMT /GLDC / GCSH (AR)

Diagnostic Test
CSF Amino Acids, Plasma Amino Acids

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SIGNS & SYMPTOMS

Neurological
Behavioral disturbances, epilepsy, ataxia, dystonia, neuropathy, unspecific mixed (cortical dysgenesis, atrophy), brain cysts / dysgenesis (MRIscan)

Non-Neurological
- - -

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THERAPY

Treatment
Glycine Restriction; +/-Sodium Benzoate, NMDA Receptor Antagonists, Other Neuromodulating Agents

Level of Evidence
4-5

Clinical Practice
Standard of Care

Treatment Effect
Stabilizes clinical deterioration; improves behaviour, seizure control & neurological manifestations



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NonKetotic Hyperglycinemia

Late-Onset Non-Ketotic Hyperglycinemia

Non-ketotic hyperglycinemia with is relatively frequent among inborn errors of newborns. It is transmitted as an autosomal recessive trait. It affects hepatic glycine cleavage, which is the main source of monocarbon radicals. Onset is generally neonatal with coma, severe hypotonia, myoclonic seizures, and microcephaly. The disease usually progresses to severe mental retardation and extrapyramidal syndrome. In the late-onset type non-specific neurological symptoms develop to varying degrees, including hypotonia, movement disorder, abnormal behaviour and movement disorder (Source: Orphanet)

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