重症筋無力症症状を呈さない抗アセチルコリン受容体抗体陽性胸腺腫の1例

Thymoma Showing Elevating Anti-acetylcholine Receptor Antibody without Clinical Symptoms of Myasthenia Gravis；Report of a Case

はじめに　抗アセチルコリン受容体抗体（抗AchR抗体）は疾患特異性が強く，重症筋無力症（myasthenia gravis：MG）の80～90％で陽性になるとされている1，2）．一方，本抗体陽性にもかかわらず，臨床的にMG関連症状を有さない症例もごくまれに報告されている．胸腺腫摘除術前に抗AchR抗体陽性が判明し，MG臨床症状を一切呈さなかった症例を経験したので報告する．

A 46-year-old man was referred to our hospital with a suspicion of pericardial cyst. Chest computed tomography （CT） revealed an anterior mediastinal tumor. He had no symptoms, but laboratory data showed positive titer to acetylcholine receptor antibody （Anti-AchR Ab）. Under a clinical diagnosis of thymoma, extended thymectomy was performed. This case may represent subclinical myasthenia gravis, so we suggest extended thymectomy is crucial for thymoma with elevated level of Anti-AchR Ab without any symptoms.