Fever of unknown origin caused by multiple myeloma: A report of 9 cases

Background: Most authorities regard multiple myeloma as a rare cause of fever and not a cause of fever of unknown origin (FUO). Objective: To describe a series of patients with FUO caused by multiple myeloma. Methods: We reviewed the clinical features of 9 patients seen at Mayo Clinic from January 1, 1975, to February 1, 2001, with FUO caused by multiple myeloma. Results: Fever of unknown origin caused by multiple myeloma was found in 9 patients (6 men and 3 women). All patients satisfied accepted criteria for FUO. The mean±SD time from the onset of fevers to the initial physician evaluation was 4.8±2.0 weeks. The mean time from the initial physician evaluation to the diagnosis of multiple myeloma was 11.4±6.5 weeks. The mean age at diagnosis of multiple myeloma was 55.9±6.9 years. All 9 patients were anemic. Peripheral blood smears were available for 8 patients, and all had rouleaux formations. All 9 patients underwent exhaustive testing to determine the cause of fevers. Further testing was done in 6 patients subsequent to the diagnosis of multiple myeloma. Acetaminophen or nonsteroidal anti-inflammatory drugs or both relieved fevers in all patients who received them. All 8 patients who received chemotherapy experienced resolution of fevers. The median actuarial survival of the patient cohort was 38 months. Conclusions: Multiple myeloma can cause FUO. When appropriate, clinicians should include multiple myeloma in the differential diagnosis of FUO to reduce unnecessary testing, rapidly establish the diagnosis, and initiate effective treatments.