Late-onset ornithine transcarbamylase deficiency associated with hyperammonemia

The urea cycle converts ammonia and produces urea. One form of urea cycle abnormality is ornithine transcarbamylase (OTC) deficiency. This hereditary disorder is associated with hyperammonemia. OTC deficiency commonly appears during neonatal and early childhood life and is rare in adults. We report a 69-year-old man who presented at the local hospital with 3-day loss of appetite, early morning vomiting, and state of confusion. Blood ammonia was 293 μg/dl. At 2-3 h after admission, the patient went into a deep coma. He was intubated and admitted immediately to the intensive care unit. Treatment, including sustained hemodialysis, failed to lower blood ammonia level. His grandchild died of OTC deficiency at 6 year of age. Computed tomography, magnetic resonance imaging and esophagogastroduodenoscopy showed no abnormalities. On admission to our hospital, he complained of vomiting and disturbance of consciousness, hyperammonemia, and normal anion gap. Genetic analysis showed A208T mutation. The deceased grandchild with OTC deficiency also had the same mutation. Long-term hemodialysis coupled with administration of L-arginine and lactulose resulted in improvement of blood ammonia level. Early diagnosis and treatment of adult-onset OTC deficiency are essential to avoid serious complications.