3-hydroxy-3-methylglutaryl-CoA lyase deficiency in an infant with macrocephaly and mild metabolic acidosis.

A girl, now three years old, is reported, in whom at the age of 5 months the diagnosis of 3-HMG-CoA lyase deficiency was established. The characteristic excretion pattern consisted of 3-HMG, 3-CH3-glutaconic acid, 3-CH3-glutaric acid and 3-HIVA. Activity of 3-HMG-CoA lyase in leucocytes was very low. She had compensated metabolic acidosis and mild hypoglycemia. Therapy with a leucine restricted diet decreased excretion of metabolites moderately but did not influence the tendency to metabolic acidosis. Clinically the infant presented with macrocephaly. At the age of 3 years she is severely retarded. CAT scan revealed the picture of progressive demyelination of the white matter.