Hyperammoniemic coma in an adolescent girl: An unusual case of ornithine transcarbamylase deficiency

Ornithine transcarbamylase deficiency (OTCD) is caused by an alteration of urea synthesis, linked with partial modification of the X-chromosome, whose clinical manifestations are: lethargy, nausea, vomiting and cerebral edema. While in newborn males OTCD presents with hyperammoniemia leading to cerebral palsy with profound neurological impairment and eventually death, in women who are healthy carriers, it is possible to detect the disorder only through specific tests, since heterozygote women are rarely symptomatic. We describe the case of a young woman admitted to the hospital after an episode of mental confusion with vomiting and psychomotor restlessness, which had previously occurred several times during the premenstruum and lasted a few hours. A 2 day history of stupor made admission mandatory. Tests carried out during the hospital stay showed marked hyperammoniemia and unconjugated hyperbilirubinemia, marked cerebral edema documented by a CT scan. Liver biopsy and CSF test were normal. Screening of plasma and urinary aminoacids, level of orotic acid in the urine and OTC activity in the liver, confirmed the diagnosis of OTCD.