Response to sodium benzoate treatment in non-ketotic hyperglycinaemia.

Therapy with benzoic acid in a case of classic neonatal non-ketotic hyperglycinaemia (NKH) was successful in stopping seizures but not in promoting mental development. Serum glycine levels were normalizable even by administering low doses of 53 mg sodium benzoate/kg body mass (BM) per day. Despite giving a higher dosage (240 mg/kg BM per day) normalization of glycine concentration in cerebrospinal fluid (CSF) was not achieved. However, seizures ceased. Restriction of protein intake (≤2 g/kg BM per day) seemed to be profitable. CSF glycine concentrations below 100 μmol/L may be sufficient to prevent seizures in older infants who have adapted to neuronal glycine exposure. No toxicity of sodium benzoate treatment was detected when administering doses of up to 470 mg/kg BM per day but side effects such as itching and hyperactivity were obvious.