A female carrier of ornithine carbamoyltransferase deficiency masquerading as attention deficit-hyperactivity disorder

Many females who are heterozygous for ornithine carbamoyltransferase (OTC) deficiency are asymptomatic or intermittently symptomatic with great phenotypic variability. Therefore, the diagnosis of this condition is occasionally a challenge and is often delayed. A 12-year-old girl who was initially diagnosed as having attention deficit-hyperactivity disorder (ADHD) became comatose and developed right-sided hemiparesis during her psychiatric admission. Brain magnetic resonance imaging indicated diffuse but extensive swelling in the left hemisphere with multiple lesions suggestive of an old infarction. Repeated evaluations revealed hyperammonemia and orotic aciduria, and she was diagnosed as having an OTC deficiency. Genetic analysis revealed a heterozygous mutation of N47I in the X-linked OTC gene. Her mental status and hemiparesis improved after hyperammonemia treatment. Here, we report a rare case of a manifestating female carrier with severe symptoms of OTC deficiency masquerading as ADHD.