Fever of Unknown Origin Caused by Multiple Myeloma

Most authorities regard multiple myeloma as a rare cause of fever and not a cause of fever of unknown origin (FUO).To describe a series of patients with FUO caused by multiple myeloma.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.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.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.