Familial hyperlysinaemia due to L-lysine alpha-ketoglutarate reductase deficiency: results of attempted treatment.

A mentally retarded male infant with persistent hyperlysinaemia due to L-lysine alpha-ketoglutarate reductase deficiency is described. The effect of dietary restriction of lysine on his mental and behavioural development was examined. By restricting daily dietary lysine to 5.5 mg/kg body weight the fasting serum lysine became normal. Urinary lysine also became normal and the secondary metabolites homocitrulline, homoarginine, N alpha-acetyllysine and N epsilon-acetyllysine were no longer detected. After control of serum lysine for 2.5 y it was felt that the patient's social behaviour, but not his mental development, had improved somewhat.