It is known that rheumatoid arthritis (RA) patients show increased incidence of multiple myeloma (MM), despite its rarity. Only one case of MM with seronegative RA was reported in Korea, thus far. We report a case of MM with seropositive RA. The patient was a 66 year old female who had been diagnosed with seropositive RA 4 years ago. Over the last 1 month, the patient experienced general weakness and weight loss of 10 kg. It was found that her serum creatinine had increased and her urine analysis showed proteinuria. To evaluate renal failure and protei-nuria, renal biopsy, bone marrow biopsy and electro-phoresis were carried out. A diagnosis of myeloma cast nephropathy was made. We report this rare case of MM represented as acute renal failure during the treatment for RA, and include a review of the literature.

Keywords: Rheumatoid arthritis, Multiple myeloma, Acute renal failure, Proteinuria