Fever of unknown origin

Abstract

This article reviews the classification and etiology of fever of unknown origin (FUO) in the adult population. A systematic diagnostic approach is discussed, equipping the NP to follow a careful history and physical, as well as focused diagnostic tests and procedures to determine the underlying cause of FUO.

Fever of Unknown Origin (FUO): towards uniform definitions and classification system

“…The current absence of a consensus on which definition for FUO is the most adequate permits many studies to use the definitions from 1961 (34)(35)(36)(37)(38) and 1991 (12,34,39,40), which makes comparisons among different studies challenging. For example, one study included 979 patients with FUO according to the definition from 1991, and only 555 of them met the criteria for FUO according to the definition from 1961 (41).…”

“…Whipple's disease is usually part of the miscellaneous group but increasingly more frequently is part of the infection category (28,36,47,55). In different reports, Castleman's disease is included in the neoplastic group (20,56), miscellaneous group (6,29,42,57,58), or infectious diseases group (47,55), and atrial myxoma sometimes is classified in the miscellaneous group (28,42,51,52) and other times is classified in the neoplastic group (5,11,36,43,55).…”

“…Whipple's disease is usually part of the miscellaneous group but increasingly more frequently is part of the infection category (28,36,47,55). In different reports, Castleman's disease is included in the neoplastic group (20,56), miscellaneous group (6,29,42,57,58), or infectious diseases group (47,55), and atrial myxoma sometimes is classified in the miscellaneous group (28,42,51,52) and other times is classified in the neoplastic group (5,11,36,43,55). In some reports, Kikuchi disease (2,9,29,50,54,57) and Crohn's disease are classified as part of the miscellaneous group (6,21,37,(55)(56)(57)59), and in other reports, Kikuchi disease (5,49) and Crohn's disease (11,33,39) are in the NIIDs group.…”

“…A normal oral temperature in 99% of the population ranges from 36.0°C to 37.7°C, with a circadian variation of 1°C or greater between the morning nadir and the evening peak. The mean oral temperature is 36.8±0.4°C, and it is slightly higher in women than in men (36.9° vs. 36.7°C) (3).…”