Acute kidney injury in a patient with polyarteritis nodosa and multiple myeloma.

We herein report the case of a Japanese man with polyarteritis nodosa (PAN) accompanied by multiple myeloma (MM). The patient was diagnosed with PAN. Concurrently, IgG kappa paraprotein was detected, and bone marrow changes indicative of MM were observed. Prednisolone (PSL) administered at a dose of 30 mg/day was initiated; however, the serum creatinine level increased. In spite of increasing the dose of PSL to 45 mg/day and initiating treatment with double filtration plasmapheresis, the patient's renal dysfunction continued to progress and haemodialysis was introduced. He died from pneumonia 12 months after admission. We conclude that renal failure is an important risk factor in the prognosis of PAN accompanied by MM.