Background: Ornithine transcarbamylase is an enzyme of the urea cycle, which produces urea from ammonia. Although ornithine transcarbamylase deficiency mainly occurs as a severe neonatal-onset disease, a late-onset form that could become symptomatic from infancy to adulthood is also known.
Case presentation: A 34-year-old man presented with sudden onset of abnormal behavior, lethargy, and hyperammonemia (108 µmol/L). He had recently increased daily protein intake, which suggested urea cycle disorder. After initiation of protein-restricted diet and treatment with arginine and sodium phenylbutyrate, his symptoms resolved, along with a decrease in the ammonia level. An R40H(c.119G > A) mutation in the OTC gene was identified.
Conclusion: Awareness of adult onset ornithine transcarbamylase deficiency in a patient with acute psychiatric symptoms due to hyperammonemia is important.
Keywords: OTC deficiency; Ornithine carbamoyltransferase.
© 2020 The Authors. Acute Medicine & Surgery published by John Wiley & Sons Australia, Ltd on behalf of Japanese Association for Acute Medicine.