Renal involvement in dermatomyositis/polymyositis

Renal lesions in polymyositis/dermatomyositis are rare and have not been clarified. In order to reveal the renal involvement in dermatomyositis/polymyositis, we performed clinicopathological study of the kidney lesion from 8 cases with dermatomyositis/ polymyositis. Proteinuria was noted in two cases; one was membranous nephropathy and the other was amyloidosis. Deterioration in renal function was noted in two cases; one was renal amyloidosis and the other was acute tubular necrosis due to rhabdomyolysis. Mucoid material was positive in the intima by Alcian blue staining and elastic fiber of the intima of the arteriole was multilayered by elastica van Gieson staining in three cases. Similar lesion was noted in small artery of the liver and the spleen from these cases. Furthermore mucoid intimal change was recognized in some of the control cases from the elder without dermatomyositis/polymyositis. These intimal changes seem to be atherosclerotic change rather than due to vasculitis of dermatomyositis/polymyositis. Various lesions should be taken into consideration in cases with proteinuria or deterioration in renal function with polymyositis/dermatomyositis.