Fatal Initial Adult-Onset Presentation of Urea Cycle Defect

Ornithine transcarbamylase (OTC) deficiency presents most commonly with neonatal hyperammonemic coma. The gene is on the X chromosome, but the disease may manifest as a dominant trait. Mutations that lead to later-onset presentations may lead to life-threatening disease and may be unrecognized, particularly when the first clinical disease occurs in adulthood.To document the clinical and metabolic consequences of a mutation in the OTC gene.Case reports.A metabolic/biochemical genetic referral service.Clinical and biochemical observations in 3 generations of a family.A mutation in codon 208 of exon 6 in the OTC gene was found in a family in which the proband died of hyperammonemia at 52 years of age.Diagnosis of late-onset presentations of urea cycle defect in adults may be delayed. Heightened awareness could lead to effective treatment.