Objective: To describe the late manifestation of partial carbamyl phosphate synthetase I deficiency in an adolescent whose previous symptoms were not distinctive enough to suggest the presence of a metabolic disease.
Research design: Clinical description of one patient.
Setting: Primary care children's hospital.
Participant: An adolescent boy.
Selection procedure: Random observation.
Interventions: Intravenous sodium benzoate and sodium phenylacetate were more successful in reversing the coma than any other intervention.
Measurements/main results: The patient has had no recurrence for 2 years, but he appears to have had a partial impairment of cognitive functioning.
Conclusions: General pediatricians and intensivists should be aware that partial carbamyl phosphate synthetase I deficiency, and other partial urea cycle disorders, may become manifest in adolescence, even though they usually present in neonates or infants. When patients present in hyperammonemic coma, the urea cycle disorders should be considered, especially if no obvious cause is identified.