Autopsy of the body of a 61-year-old man with rheumatoid arthritis shows enlarged and dense yellow-while kidneys with a waxy sheen and areas of dcatridal depressions on their surface. Congo red staining reveals deposition of homogeneous pink masses in the capillary loops of the glorneruli, in the walls of the arterioles and arteries, in the basement membrane of the tubules, and in the stroma. In this case, rheumatoid arthritis was complicated by the development of the following proses: glornerulonephritis