Abstract
Both general practitioners and hospital physicians encounter patients with febrile febrile illness, the cause of which is not obvious. Fever of unknown origin (referred to in the Anglo-Saxon literature by the abbreviation FUO according to Fever of Unknown Origin) is almost always a diagnostic problem, as the diseases that can cause it are very diverse and are the domain of several medical disciplines.
An older definition of fever of unclear origin according to Petersdorf and Beeson is given in the article. The diagnosis of febrile illness should be made within seven days of the hospitalized patient.
According to the newer definition of Durack and Street, which the authors of the article also cite, the cause of febrile illness should be found during a three-day hospitalization or during three outpatient examinations, then the patient's disease falls into the category of fever of unclear origin. However, in the real conditions of most inpatient wards, it could be difficult to organize all the necessary examinations and obtain results within three days of hospitalization, the seven-day limit seems more realistic.
The authors of the article deal mainly with the classic fever of unclear etiology. This category includes feverish patients for whom no immunodeficiency is known at the onset of febrile illness and who are not hospitalized in inpatient wards at possible risk of nosocomial infection.
Another situation is the group of HIV positive or neutropenic patients (Table 1). Fever of unclear origin may have an infectious etiology, as well as oncological or autoimmune diseases and other causes.
The proportion of these diseases varies in different age groups. Patients older than 65 years are more likely to cause febrile malignancies and connective tissue diseases than younger patients.
Infection predominates in children. Due to the duration of the problem, the probability of infectious etiology decreases.