RT Journal Article SR Electronic T1 Fever of unknown origin JF Clinical Medicine JO Clin Med FD Royal College of Physicians SP 280 OP 284 DO 10.7861/clinmedicine.15-3-280 VO 15 IS 3 A1 Catharina Mulders-Manders A1 Anna Simon A1 Chantal Bleeker-Rovers YR 2015 UL http://www.rcpjournals.org/content/15/3/280.abstract AB More than 50 years after the first definition of fever of unknown origin (FUO), it still remains a diagnostic challenge. Evaluation starts with the identification of potential diagnostic clues (PDCs), which should guide further investigations. In the absence of PDCs a standardised diagnostic protocol should be followed with PET-CT as the imaging technique of first choice. Even with a standardised protocol, in a large proportion of patients from western countries the cause for FUO cannot be identified. The treatment of FUO is guided by the final diagnosis, but when no cause is found, antipyretic drugs can be prescribed. Corticosteroids should be avoided in the absence of a diagnosis, especially at an early stage. The prognosis of FUO is determined by the underlying cause. The majority of patients with unexplained FUO will eventually show spontaneous remission of fever. We describe the definition, diagnostic workup, causes and treatment of FUO.