[Fever of unknown origin caused by multiple myeloma. Report of one case].

Fever of unknown origin (FUO) can be caused by tumors, especially those arising from the hematopoietic system. Multiple myeloma can also cause fever but it is not a common cause of fever of unknown origin. We report a 53 year-old man presenting with fever lasting eight weeks. An extensive study for common causes of FUO was negative. The appearance of hypercalcemia and proteinuria during the evolution suggested the presence of a multiple myeloma, that was confirmed with a bone marrow biopsy. Thalidomide and dexametasone were prescribed with resolution of fever.