慢性移植片対宿主病（慢性GVHD）の経過中に多発性筋炎を発症したと考えられる一例

Polymyositis is an uncommon manifestation as a complication of chronic graft-versus-host disease (GVHD). We report a case of a 55 years' old woman diagnosed as polymyositis 2 years after bone marrow transplantation against T-cell lymphoma. Muscle weakness and the elevation of CPK value were compatible with pathognomonic findings of polymyositis. However, the muscle weakness was distributed particularly into distal lower extremities and neck. It is different from that of the typical findings in autoimmune polymyositis. Histological findings showed atrophy and anisocytosis of muscles without invasion of mononuclear cells. This might be a case of GVHD-induced polymyositis occurring symptomatically after substantially progressing under the treatment with immunosuppressive agents to control chronic GVHD after bone marrow transplantation. The treatment with prednisone (1 mg/kg) brought the rapid improvement of muscle weakness and CPK value as well as mouth dryness and cholestatic liver dysfunction like in primary biliary cirrhosis. Moreover, dose up of cyclosporine and addition of mizolibine allowed for the use of lower dose of prednisone. This case suggested that the mononuclear cells invasion into muscles in a chronic GVHD patient could not always be a definitive finding of chronic GVHD-associated polymyositis because of prior use of immunosuppressive agents.