Late onset ornithine transcarbamylase deficiency in a 61 year old male

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Ornithine transcarbamylase (OTC) deficiency is the most frequent innate urea cycle disorder (UCD) and is the only one with an X-linked inheritance. OTC deficiency leads to hyperammonemia and subsequent elevated cerebral pressure and brain damage. Most often, UCDs are described as acute onset hyperammonemia in the newborn; however, rare, it can present in adulthood. We present the case of a 61-year old Caucasian man with unexplained coma. He developed an acute hyperammonemic encephalopathy leading to mental problems, seizures and coma. Despite the classical treatment with hemodialysis and the administration of a combination of sodium phenylacetate and sodium benzoate, the patient unfortunately died of cerebral herniation. Postmortem, genetic analysis confirmed the presence of a c.662G > A (p.Ala208Thr) pathogenic mutation in the OTC gene in a hemizygous state. Synopsis: The association of neuropsychiatric symptoms or encephalopathy of unknown origin should lead, even in the absence of liver disease and even in late adulthood, to a high level of suspicion of hyperammonemia secondary to UCDs to ensure a timely diagnosis and life-saving treatment. UCD, an inborn error of metabolism, can present itself at an advanced age; attenuated phenotypes probably remain under-ascertained.