[Adenocarcinoma of the prostate associated with anti Jo-1 antibody positive polymyositis].

A 76-year-old male was hospitalized with elevation of prostate specific antigen. We closely examined him further because creatine phosphate kinase was found to be 2,841 IU/l in the pre-operative examination. He was positive for anti Jo-1 antibody, and was found to have muscular atrophy of lower extremities on magnetic resonance imaging, and fibrillation and positive sharp waves on the electromyogram. He was therefore diagnosed with polymyositis. Adenocarcinoma was classified as Gleason score 8 by needle biopsy of the prostate and the stage of the prostate carcinoma was cT3aN1M0. The patient was treated with hormonal ablation and oral steroids.