74 歳男性.顔面,四肢,体幹の紅斑に続き,構音障害および嚥下障害,四肢筋肉痛並び脱力が出現し,起立困難となり入院となった.CK, ALD, AST, LDH 等筋原性酵素の著明上昇及び臨床所見により皮膚筋炎と診断された.高用量ステロイド療法その後シクロスポリンの追加にて治療開始し,検査所見に続き,臨床所見も改善傾向にあった.同時にproGRP 高値並びに全身CT 画像上縦隔リンパ節腫大認め,気管支鏡下気管支粘膜生検にて小細胞肺癌の病理診断が得られ,CBDCA+CPT-11 にて化学療法を施行,腫瘍の縮小効果を見た.皮膚筋炎が腫瘍随伴症候として,小細胞癌とほぼ同時期に発病したことを示唆した症例であったA 74-year-old man was admitted because of erythemaon face, extremities and trunk, followed by dysarthria, dysphagia,extremity myalgia accompanied with weakness, andthen difficulty in upstanding. Dermatomyositis (DM) wasdiagnosed on the basis of a marked increase in serum levelof myogenic enzymes, such as creatinin kinase, aldolase, aspartateaminotransferase and lactate dehydrogenase, andthe clinical manifestations. Introduction of high-dose glucocorticoidtherapy, subsequently concurrent administrationof cyclosporin, made laboratory data gradually return tonormal and produced slight symptom improvement. Inscreening for malignancies, high level of proGRP detectedin peripheral blood, computed tomography scan showed mediastinallymphadenopathy, and histopathologial testing ofthe transbronchial biopsy specimens revealed small celllung cancer (SCLC). Chemotherapy (CBDCA+CPT-11)started, resulting in tumor reduction. The current case maysuggest that DM coincided with SCLC around at the sametime, as a mean of paraneoplastic syndrome