Fever of Unknown Origin

According to the publication in StatPearls NCBI Bookshelf, fever of unknown origin (FUO) was first described in 1961 by Dr. Petersdorf and Dr. Beeson. This puzzling condition often involves common symptoms presenting in an atypical manner. The list of potential causes is extensive and can be categorized broadly into infections, noninfectious inflammatory conditions, malignancies, and miscellaneous factors. Diagnosing FUO is no easy task, lacking a definitive approach. To unravel the mystery, a comprehensive patient history should not neglect information about prior illnesses, localizing symptoms, alcohol consumption, medications taken at home, occupational exposures, pet interactions, travel history, and familial disorders. In the clinical setting, it is crucial to verify the presence of fevers and analyze their patterns. This scrutiny can provide valuable hints regarding specific infectious triggers.
During the differential diagnosis process for FUO, it is essential to bear in mind that the cause is more likely to be a subtle or atypical manifestation of a common disease rather than a rare one. As part of the initial diagnostic testing, certain essential examinations should be conducted, including a complete blood count with a differential, a complete metabolic panel, a urine analysis with microscopy and urine culture, three sets of blood cultures, a chest radiograph, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) assessment. For further details, you can find additional information through the provided link.