Objective: To report an atypical presentation of medium-chain acyl Coenzyme A dehydrogenase deficiency in a 13-year-old girl with hyperammonemic encephalopathy and orotic aciduria meeting the accepted criteria for diagnosis of a female heterozygous for ornithine transcarbamylase deficiency.
Design: Case report and definitive biochemical testing.
Setting: Children's hospital and university laboratory.
Participant: One teenager.
Interventions: Diagnosis and treatment with carnitine.
Measurements/main results: Assay ornithine transcarbamylase deficiency had normal results. The diagnosis was confirmed by DNA analysis, which revealed homozygosity for prevalent mutation (the adenine to guanine transition at position 985).
Conclusions: Patients with a clinical diagnosis of Reye's syndrome have, in general, an inborn error of metabolism. Medium-chain acyl Coenzyme A dehydrogenase deficiency and other disorders of fatty acid oxidation may present long after infancy. They may mimic the presentation of defects in the urea cycle.