Abstract OBJECTIVE: To review the etiology of fever of unknown origin (FUO) and the methods used to establish a diagnosis. METHODS: A retrospective review of the medical records of 317 patients with FUO admitted between January, 1996 and December, 2000 was performed. RESULTS: Of the 317 children, 298 cases (94.0%) had a definitive etiology established. Of the 298 cases, 160 (53.7%) had infectious diseases and non infectious diseases, such as collagen vascular disease, and neoplasm which accounted for a large fraction of the remainder. A diagnosis was established in 140 (47.0%) by comprehensive clinical analysis alone. Culture of bacteria in serum and biopsy specimens established a diagnosis in 64 cases (21.5%) and 37 cases (12.4%), respectively. Noninvasive imaging techniques (35 cases; 11.7%), autopsy (11 cases; 3.7%), bone marrow examination (6 cases; 1.9%) and retrospective diagnosis (5 cases; 1.7%) accounted for the remainder of the diagnosis. CONCLUSIONS: Most cases of FUO can be diagnosed by clinical characteristics of the patients and by essential laboratory studies. Pathological examination is very important in diagnosing the etiology of FUO. Infectious diseases, collagen vascular disease and neoplasm are the major causes of FUO in children.
