Fever of unknown origin (FUO) represents a diagnostic challenge to many physicians and while cancer and infectious causes need to be excluded, rheumatic disorders are amongst the most common causes of FUO.
A recent metanalysisi of the medical literature from 2002 to 2021, included studies with ≥50 patients reporting on causes of FUO/IUO (inflammation of unknown origin). This series included 16884 patients.
Rheumatic etiologies were found in 22% of cases; lead by adult-onset Still’s disease (AOSD – 22.8%), giant cell arteritis (11.4%), and systemic lupus erythematosus (11.1%).
Rheumatic causes of FUO were significantly higher with higher vs lower-income countries (25.9% vs. 19.5%) and in prospective studies (27% vs 20.6% retrospective studies). According to multivariable meta-regression analysis rheumatic disease was associated with the duration of fever (P=0.01).
Rheumatologists are likely to be engaged in the evaluation and care of those considered to have FUO or IUO.