Background: The etiology of fever of unknown origin (FUO) includes primarily infectious, collagen-vascular and neoplastic diseases. The distribution of the disorders causing FUO may differ according to the geographic area and the socioeconomical status of the country. Moreover, the developments in radiographic and microbiologic methods have changed the spectrum of diseases causing FUO.
Materials and methods: We reviewed 117 cases that fulfilled the criteria of FUO followed in our department during the period 1984 to 2001.
Results: The etiology of FUO was infectious diseases in 34% of the patients, collagen-vascular diseases in 23%, neoplasms in 19% and miscellaneous diseases in 10%. In 14% of the cases the etiology could not be found. The three leading diseases were tuberculosis (24%), lymphomas (19%) and adult-onset Still's disease (11%). Tuberculosis was found to be a more common cause of FUO than reported in studies in developed countries. Invasive procedures helped to establish the diagnosis in 50 out of 92 patients (43%). As a final diagnostic procedure, laparotomy aided the establishment of a diagnosis in 15 out of 20 patients (75%).
Conclusion: Although the relative rate of infectious disease as etiologic category is less commonly encountered, infectious disease, especially tuberculosis, remains a common cause of FUO. Although several diseases may lead to FUO, lymphomas, adult-onset Still's disease and particularly tuberculosis should be considered in the differential diagnosis of a patient admitted with FUO.