Non-ketotic hyperglycinemia (NKH). Infantile form.
Incidence
Has been reported in ~ 20 cases. Also a primary glycine cleavage system defect in the liver.
Clinical Characteristics
Patients are normal during the first 2-6 months, then on the 2nd part of first year, may be progressive dementia and decerebrate rigidity. Extrapyramidal signs are not uncommon. Often pts. are mildly retarded, with tremor, seizures, hypotonia.Twitching . Developmental delay, MR, hyperactivity, expressive speech deficit. The EEG shows high voltage slowness diffuse. Plasma glycine levels lower than neonatal form but CSF & CSF/Plasma ratio is abnormally high.
Precipitants
Intercurrent infections or mild head traumas may trigger severe difficult to control seizures.
Provocation Tests
no
Diagnostic Procedures
CSF and plasma glycine. EB-liver. The ratio of CSF glycine to plasma glycine is much higher than in patients with organic acidurias (0.1-0.3; normal 0.01-0,03)