Fever of unknown origin in adults: 40 years on

Abstract

A revision of the criteria of fever of unknown origin (FUO), established in 1961, is desirable because of important evolutions in medical practice and the emergence of new patient populations. The development of rapid laboratory tests and powerful diagnostic tools, such as ultrasonography, computed tomography and magnetic resonance imaging often makes hospitalization unnecessary and new categories of patients such as those with HIV infection, neutropenia, immunosuppression and nosocomial illness require an approach different from classical FUO. The more then 200 reported causes of FUO can be classified into four diagnostic categories; infections, tumours, noninfectious inflammatory diseases (NIID) and miscellaneous. A uniform classification system is highly wanted to allow comparison between different series. The reports of the 1990s show slight changes in the distribution of causes, namely less infections, less tumours, more NIID and more undiagnosed cases. A uniform diagnostic strategy cannot be determined. The initial investigation should be directed by potentially diagnostic clues revealed by extensive history, meticulous physical examination and a standard set of laboratory tests.18 Fluoro-deoxy-glucose-positron-emittedtomgraphy is a new valuable total body scintigraphy in the search for the site of origin of the fever. In view of the rather good long-term prognosis, a wait-andsee strategy may be more appropriate than a systematic staged approach. Elderly patients and patients with episodic fever represent two specific groups of classical FUO that require a distinct approach. HIVassociated, nosocomial and neutropenic FUO should be considered as separate clinical entities.

Fever of unknown origin

“…These causes can be subdivided in four categories: infections, malignancies, non-infectious infl ammatory diseases (NIID, this group includes autoimmune and rheumatic diseases, vasculitis syndromes and granulomatous disorders) and miscellaneous causes. 3,6 Overall, uncommon presentations of common diseases account for most cases.…”

FDG-PET Imaging in HIV Infection and Tuberculosis

“…HIVassociated FUO can be defined as "fever 38.31C or higher on several occasions, in a patient with a confirmed positive serology for HIV, with a duration of fever of 4 weeks or more for outpatients, or 3 days or more for hospitalized patients, with an uncertain diagnosis after 3 days despite appropriate investigation, including at least 2 days' incubation of microbiological cultures." 37,38 Patients with HIV have an increased risk of fever owing to multiple factors. Infection with HIV itself can cause fever, 39 as is the case in 40%-90% of patients with HIV primoinfection.…”

Fever of unknown origin: large vessel vasculitis diagnosed by PET/CT

“…Large vessel vasculitis represents about 17% of all FUO cases among patients over 50 years of age [3,4]. GCA is the most common cause of large vessel vasculitis, predominantly involving the proximal aorta and its branches, and characterized by a granulomatous inflammation of the vessel wall [5].…”

“…A variety of possible clinical entities should be considered in the workup of FUO: infectious diseases, chronic granulomatous non-infectious diseases, oncological and hematological diseases, as well as inflammatory rheumatic conditions, including connective tissue diseases and vasculitides [2,3,4].…”