Neonatal hyperammonemia associated with carnitine deficiency.

We report a case of neonatal hyperammonemia associated with secondary carnitine deficiency. She suffered from hyperammonemia soon after the birth, and then presented severe metabolic acidosis at 2 months of age. She was successfully treated for acidosis with oral administration of L-carnitine (100 mg/kg/day). Since hyperammonemia recurred with the increase of protein intake, it was necessary to increase the dose of carnitine to 150 mg/kg/day. Urea cycle enzymopathies were excluded from the laboratory data. The urinary organic acid profiled by gas chromatography mass spectrometry revealed no abnormalities. It was found that the carnitine contents in serum urine and muscle were decreased. After we investigated the carnitine status in other members of the family, the brother of this patient, who had died of metabolic acidosis and hyperammonemia of unknown etiology in the neonatal period, was also revealed to have carnitine deficiency. Since specific enzyme defects which caused secondary carnitine deficiency could not be detected in our patients, further biochemical characterization would be necessary to clarify the cause of hyperammonemia.