アセトアミノフェン服用後に発症したII型シトルリン血症の1例

Type II Citrullinemia Triggered by Acetaminophen

　II型シトルリン血症は肝のアルギニノコハク酸合成酵素の量的低したに基づ疾患であるが，成人で発症する原因については不明な点が多い。我々は，感冒時にアセトアミノフェン服用後に発症した本疾患の1例を経験し，また発症誘因に関して過去12年間28症例の文献的検索を行い，若干の考察を加えて報告する。症例は19歳の男性。不穏・意識障害で発症した。初診時，中枢性過呼吸による呼吸性アルカローシスを呈し，高アンモニア血症が認められた。血漿・尿アミノ酸分析にてシトルリンが異常高値を示した。症状は脳波所見とよく相関し，意識障害に対して分枝鎖アミノ酸製剤が，高アンモニア血症に対して安息香酸ナトリウムが有効であった。肝生検にて肝の炎症所見を認めた。文献的検索から発症誘因を1：ストレス，2：肝機能障害，3：飲酒，4：薬物の4っに分類した。本疾患の予後を決定するうえで，早期診断および治療と発症誘因の回避が重要な問題と考えられた。

We report a 19-year-old man with type II citru-llinemia triggered by the administration of acetaminophen when he caught a cold. He was admitted to our hospital of impairment of conscious-ness and abnormal behaviors. On admission he was comatose and laboratory data revealed respiratory alkalosis which was probabley induced by hyperam-monemia. Liver dysfunction was mild. Plain CT scans showed brain edema, and EEG revealed tri-phasic waves. Analysis of plasma and urine amino acids showed a significant increase in citrulline and the activity of argininosuccinate synthetase was markedly reduced in a liver biopsy specimen. Histopathology of the liver revealed inflammatory changes which was probably induced by acetamino-phen. Branched chain amino acids transfusion was effective for consciousness disturbance, and sodium benzoate was effective for hyperammonemia. We reviewed 28 patients reported in the literature from 1981 to 1992 to evaluate the probable triggering episodes in type II citrullinemia. Four categories of probable trigger were found, which included 1) stress, 2) liver dysfunction, 3) alcohol, and 4) drugs. Avoidance of these triggers, early diagnosis, and treatment seem most important for the good prog-nosis and the quality of life.