[Fever of unknown origin in rheumatology]

Fever occurs frequently in several rheumatic disorders, and remains a diagnostic and therapeutic challenge to the rheumatologist in spite of the great advances made in the fields of medical diagnosis and technology. It can be the initial symptom of a rheumatic disease, but it can also be the expression of a disease flare, of an infectious complication, of a secondary neoplasm or be of iatrogenic origin. The pathogenesis of fever in rheumatic diseases is still quite unclear; however, recently IL-1, IL-6 and other endogenous pyrogens, such as Tumor necrosis factor, have been shown to play a pivotal role in causing pyrexia during inflammatory conditions. In the presence of longstanding fever of unknown origin, it is mandatory to carry out a number of selected appropriate examinations with the patient's informed consent. The aim of this study was to review the frequency and the characteristics of fever at the onset and in the course of a number of rheumatic diseases, such as chronic inflammatory arthropathies, connective tissue diseases, reactive arthritis and dysmetabolic arthropathies. Finally, we have reviewed the features of fever during arthritis complicating non-rheumatic diseases and during adverse reactions related to drugs that are widely prescribed for the treatment of rheumatic disorders.