A 71-year-old woman with adult-onset type II citrullinemia, initially presenting with normal blood ammonia levels

The patient, a 71-year-old woman, was admitted for a generalized tonic-clonic seizure. Initial investigations, including plasma ammonia, were normal, and she was treated for status epilepticus. Consciousness recovered to Japan Coma Scale (JCS) 0, but on day 4 her alertness declined; plasma ammonia exceeded 500 ‍μg/dl, and a dietary preference for beans became apparent. Plasma citrulline was markedly elevated, and genetic analysis confirmed adult-onset type II citrullinemia (CTLN2). A low-carbohydrate, high-fat diet enriched with medium-chain triglyceride oil was initiated, yet higher order cognitive deficits persisted. Because CTLN2 exhibits diurnal fluctuations in blood ammonia, in cases of unexplained impaired consciousness it is essential to ask about food preferences and to measure plasma ammonia repeatedly to enable timely diagnosis and treatment.