Vomiting, ataxia, and altered mental status in an adolescent: late-onset ornithine transcarbamylase deficiency.

A case of a 13-year-old boy with protracted vomiting, ataxia, and altered mental status, ultimately diagnosed with late-onset ornithine transcarbamylase (OTC) deficiency, is presented. OTC deficiency is the most common urea cycle defect and typically is diagnosed in male infants with irritability, poor feeding, vomiting, lethargy, and often death caused by the effects of hyperammonemia. Late-onset OTC deficiency has been described in patients of all ages. The presenting symptoms in these patients vary but the most common are vomiting and lethargy. The pathophysiology, clinical features, differential diagnosis, and treatment of this disorder are discussed. Because of the risks of serious consequences, early detection and treatment of OTC deficiency and hyperammonemic episodes are mandatory. Emergency physicians caring for children and adults need to be aware of the spectrum of clinical presentations of OTC deficiency, including late-onset disease.