Fatal hyperammonemia after repeat renal transplantation

•Hyperammonemia may occur despite normal hepatic function.•Untreated hyperammonemia may lead to cerebral edema, intracranial hypertension, and irreversible neurologic sequelae.•Management of hyperammonemia includes increasing the excretion of ammonia, decreasing exogenous nitrogen and ammonia production, and providing alternative pathways for ammonia excretion.

A 35-year-old man had symptomatic hyperammonemia and normal liver function after repeat kidney transplantation. He presented with gastrointestinal symptoms, which quickly progressed to altered mental status. Therapy was instituted to clear the ammonia, but the ammonia level continued to rise. Eventually, the patient became unresponsive, and an emergent computed tomographic scan showed cerebral herniation. Urine acids and serum organic acids were not diagnostic of any urea cycle disorder. Histology did not reveal a clear etiology for the hyperammonemia.