封入体筋炎に慢性甲状腺炎，Sjogren症候群，自己免疫性胆管炎を合併した1例

摘要

症例は67歳女性。 両大腿部の筋萎縮を主訴として来院。 筋萎縮は大月退四頭筋にほぼ限局しており，いわゆる大腿四頭筋ミオパテーの臨床像を呈していた。 血清クレアチンキナーゼ値の上昇を認めず，筋生検にて筋内鞘から筋線維内部への炎症細胞浸潤，綾取り空胞，赤色ぼろ線維などの特徴的な所見が確認されたことから封入体筋炎（IBM）と診断した。 本例は，慢性甲状腺炎，Sjogren症候群，自己免疫性胆管炎など複数の自己免疫疾患を合併しており，本例におけるIBMの病態に自己免疫異常が関与している可能性が考えられた。 A 67-year-old woman was admitted to our hospital, because of wasting of the thigh muscles. Muscular atrophy was confined to the thigh muscles, suggesting that she had quadriceps myopathy. Muscle biopsy from quadriceps muscle revealed characteristic findings, such as invasion of the endomysium and muscle fibers by inflammatory cells, the presence of rimmed vacuoles and ragged red fibers; thereby, she was diagnosed as having inclusion body myositis(IBM). Based on elevated titers of autoantibody as well as biopsy findings from salivary gland and liver, she was also diagnosed as having chronic thyroiditis, Sjogren's syndrome and autoimmune cholangitis. Currently, the pathogenic mechanism underlying IBM is not clarified, however, various factors have been suggested to contribute to it, such as viral infection or mitochondrial insufficiency. Although the pathogenic backgrounds underlying IBM are likely heterogeneous, an autoimmune-mediated mechanism may be related to the pathogenesis of IBM in the present patient.