[A case of myeloma kidney complicated by extramedullary plasmacytoma with massive bleeding]

A 76-year-old woman, who had received hemodialysis due to chronic renal failure of unknown cause for two months, was admitted to our hospital. She was suffering from severe pain in the left thigh, rapidly progressive anemia and thrombocytopenia after receiving a contusion on her left thigh. Soon after admission, the patient died of shock. Autopsy revealed multiple myeloma(lamda type) with extramedullary plasmacytoma and systemic amyloidosis. In the kidney, there were typical tubular casts with multinucleated giant cells and interstitial fibrosis. More specific findings included an extramedullary plasmacytoma in the left iliopsoas muscle surrounded by a huge hematoma. Internal hemorrhage resulting from indirect contusion at this site was likely to have caused her shock. Since typical clinical findings of multiple myeloma, such as serum M protein and hypercalcemia, were not found in this case, it was difficult to make a diagnosis of multiple myeloma. In case of multiple myeloma, micro- or macroscopic extramedullary tumor formation is not rare, but there has been no report of a case with macroscopic tumor formed in skeletal muscle, exhibiting massive hemorrhage. We report here a case of multiple myeloma with an unusual clinical course.