Hyperammonemic Coma in an Adult due to Ornithine Transcarbamylase Deficiency

Objective. To report an unusual cause of coma in an adult. Design. Case report. Setting. University teaching hospital. Patient. A previously healthy 53-year-old man initially presented with altered mental status and progressed to coma. He was found to be substantially hyperammonemic and did not improve with lactulose therapy and continuous venovenous hemodialysis. Results. Biochemical testing revealed previously undiagnosed ornithine transcarbamylase deficiency, and the patient responded to arginine, sodium phenylacetate, and sodium benzoate. Conclusion. Even in adult patients with no known history, inborn errors of metabolism must be considered in the differential diagnosis of unexplained coma. Defects of the urea cycle can present with an unprovoked hyperammonemic coma. 1. Introduction The differential diagnosis of coma in adults is notoriously broad, but the presence of hyperammonemia narrows it to Reye’s syndrome, high-dose chemotherapy, Proteus infection, glycine toxicity (after transurethral resection of prostate) [1], liver failure, and late-onset urea cycle defects [2]. Although disorders of the urea cycle are predominantly the purview of the neonatologist, presentations of urea cycle enzyme deficiencies in adults have been reported. 2. Case Report A fifty-three-year-old man was admitted to an outside hospital with a significantly decreased level of consciousness. He had awoken at night and urinated on the bathroom floor, and the following morning, his wife was unable to fully awaken him. He had reported progressive fatigue over the preceding two weeks, but had otherwise been in his usual state of good health. Specifically, he had no history of fevers, chills, rigors, weight loss, chest pain, shortness of breath, nausea, vomiting, or abdominal pain. His past medical history was significant only for benign prostatic hypertrophy and hyperlipidemia. He had no history of alcohol abuse, diabetes mellitus, or liver disease. His medications included terazosin, tamsulosin, and a recent methylprednisolone taper for a nonspecific groin rash. He had initiated therapy with simvastatin approximately one month prior to admission. His only recent toxin exposure was the use of a permethrin-based insecticide, and he reported no symptoms during or after this exposure. On admission to the outside hospital, the patient was afebrile and anicteric with normal vital signs. The neurologic examination revealed that he was only intermittently arousable to verbal stimuli, with the remainder of the exam being nonfocal. A complete blood count, serum electrolytes, serum