A case of type I cryoglobulinemia associated with a monoclonal gammopathy of undetermined significance (MGUS).

A 79-year-old Japanese male who had been suffering from renal insufficiency of unknown causes visited us with reddish papules and purpura on both forearms of a month's duration. A skin biopsy was performed from the right forearm, and the histopathology showed an obstruction of superficial blood vessels with eosinophilic amorphous materials suggesting cryoglobulins. Although further investigations revealed the presence of monoclonal immunoglobulin (Ig) G-kappa type I cryoglobulin, a bone marrow biopsy demonstrated that there was 7.6% proliferation of plasmacytoid cells, and the serum level of Ig G was less than 3 g/dl. The diagnosis was type I cryoglobulinemia associated with monoclonal gammopathy of undetermined significance as the possible cause of chronic renal failure. Therefore, purpuric changes on extremities of the elderly, especially those complaining of renal failure should, be taken seriously and not regarded simply as an age-related phenomenon.