Fever of unknown origin (FUO) and inflammation of unknown origin (IUO) are among the most complex and challenging clinical syndromes in Internal Medicine. Internists, by virtue of their broad expertise across the whole spectrum of adult diseases, serve as the cornerstone specialists in the diagnostic evaluation of FUO/IUO, orchestrating structured and methodical diagnostic processes. This thorough approach is essential to avoid unnecessary tests or treatments and narrow down the differential diagnosis [1].
