A case of transient neonatal citrullinemia.

A male infant with transient citrullinemia is described. Initially, he was found to have hypertyrosinemia and hypermethioninemia upon routine neonatal screening for inborn errors of metabolism performed at 4 days of age and was revealed to have citrullinemia upon detailed examination of plasma amino acids. At 30 days of age, the plasma citrulline concentration was 13 mg/dl (normal, less than 0.8). In addition, the citrulline concentrations in the urine and cerebrospinal fluid (CSF) were markedly elevated. The blood ammonia and the CSF ammonia concentrations (300 micrograms/dl and 59 micrograms/dl, respectively) were also increased, but the infant showed no symptoms. Dietary protein intake was restricted to 2 g/kg/day, resulting in normalization of plasma citrulline and blood ammonia concentrations by 2 months of age. At 12 months of age, the infant was given a regular diet, and his physical and mental development was normal. 14C-citrulline incorporation into trichloroacetic acid (TCA)-precipitable material was normal in the fibroblasts. This report describes the first case in the literature of transient neonatal citrullinemia.