ステロイド療法中止後に再燃を繰り返したアミオダロン肺障害の1例

Repeated Relapses of Amiodarone Induced Pulmonary Toxicity after Withdrawal of Corticosteroid Therapy

要旨　患者は58歳，男性．2007年10月，近医にて大動脈閉鎖不全症，僧帽弁閉鎖不全症，慢性心房細動に対し大動脈弁置換術，僧帽弁置換術，左房メイズ術，左房縫縮術，左室側壁心筋リード縫着術を施行．術後よりアミオダロン200mg/日で洞調律を維持していた．2008年12月に呼吸困難を発症し前医を受診した．胸部CTでは両側下肺野にスリガラス様陰影を認め，アミオダロン肺障害と診断された．同剤の中止，ステロイドパルス療法により一時的に酸素化は改善したが，再燃したためステロイドパルス療法が繰り返し行われた．当院転院時，薬剤中止から3カ月経過したにもかかわらず，アミオダロン血中濃度は400ng/mlと高値であった．以降ステロイド減量に際し，アミオダロン血中濃度のモニターが参考となった．アミオダロンは半減期が長く少量投与であっても組織中に蓄積するため，ステロイド減量については慎重に行う必要がある．

　A 58 year-old male visited a hospital with dyspnea on December, 2008. One year and two months before his visit, he had undergone aortic valve replacement, mitral valve replacement,Maze operation,left atrium plication and lead implantation for aortic regurgitation, mitral regurgitation and chronic atrial fibrillation. After the operation, 200mg/day of amiodarone was administered. Since his chest CT revealed ground glass opacity in the lower lung field, he was diagnosed as having amiodarone-induced pulmonary toxicity. Amiodarone was discontinued and 500mg of methylpredonisolone was administered intravenously for 3 days. Although he showed temporary improvement, rapid withdrawal of corticosteroid therapy led to deterioration of his pulmonary condition. When he was referred to our hospital in March, 2009, the plasma amiodarone concentration remained as high as 400ng/ml. The monitoring of the plasma amiodarone concentration was useful for the tapering off of corticosteroid. Careful reduction of corticosteroid is recommended because amiodarone tends to accumulate in tissues and has a long half-life period.