Multiple myeloma presenting as acute tubulointerstitial nephritis and normal serum protein electrophoresis.

Multiple myeloma is uncommon in individuals younger than 40 years. Renal involvement is common in this disease, but acute tubulointerstitial nephritis is very rare. In 20% of patients, only the light chain is produced and serum protein electrophoresis is normal; however, in urine protein electrophoresis of these patients, the M spike is present. We reported a case of multiple myeloma in a 39-year-old man with acute tubulointerstitial nephritis. Serum protein electrophoresis was normal and there was no bone lytic lesion. Remission of multiple myeloma was achieved after treatment with thalidomide and dexamethasone; however, kidney failure was not improved and the patient was maintained on hemodialysis.