An Unusual Presentation of Medium-Chain Acyl Coenzyme A Dehydrogenase Deficiency

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. —Case report and definitive biochemical testing. —Children's hospital and university laboratory. —One teenager. —Diagnosis and treatment with carnitine. —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). —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.