Late-onset ornithine transcarbamylase deficiency: a potentially fatal yet treatable cause of coma.

Hyperammonaemia due to ornithine transcarbamylase (OTC) deficiency is a well-described cause of coma in neonates. Rarely, adults with this disorder may also present with coma. Here we describe the first reported case, to our knowledge, in a pregnant woman. She was successfully treated with metabolic therapy and, contrary to usual paediatric practice, renal replacement therapy. We review the biochemistry of OTC deficiency and other urea cycle disorders, and discuss the physiological rationale and evidence base for treatment of this condition. We highlight the need to consider hyperammonaemia in the differential diagnosis of coma.