Successful treatment of severe carbamyl phosphate synthetase I deficiency.

We describe a girl with neonatal hyperammonaemia due to carbamyl phosphate synthetase I deficiency. Treatment consisted of protein restriction from the second day of life. Sodium benzoate was given for three weeks after birth and again from 7 months of age together with sodium phenylacetate to improve protein tolerance. Growth and development are normal at 15 months of age.