An adult-onset case of argininosuccinate synthetase deficiency presenting with atypical citrullinemia

A 52-year-old heavy drinker presented with repeated episodes of disturbance of consciousness and an increase in serum ammonia level, triggered by exce ssive alcohol intake. He was diagnosed as having adult-onset citrullinemia with deficiency of hepatic argininosuccinate synthetase (ASS) activity. Cra nial magnetic resonance imaging (MRI) showed high-intensity lesions in the central pens and the bilateral middle cerebellar peduncles on T2-weighted i mages, Although almost all cases of adult-onset citrullinemia have been rep orted to be enzymologically classified as type II, the serum amino acid pat tern and serum level of human pancreatic secretory trypsin inhibitor (hPSTI ) were atypical for type II in the present case.