Fever of unknown origin in special groups

Abstract

SUMMARY Fever of undetermined origin (FUO) is a challenging entity with a striking presence in hospitals around the world. It is defined as temperature ≥ 37.8 ° C on several occasions, lasting ≥ three weeks, in the absence of diagnosis after three days of hospital investigation or 3 outpatient visits. The main etiologies are infectious, neoplastic, and non-infectious inflammatory diseases. The diagnosis is based on the detailed clinical history and physical examination of these patients, in order to direct the specific complementary tests to be performed in each case. The initial diagnostic approach of the FUO patient should include non-specific complementary exams. Empirical therapy is not recommended (with few exceptions) in patients with prolonged fever, as it may disguise and delay the diagnosis and conduct to treat the specific etiology. The prognosis encompasses mortality of 12-35%, varying according to the baseline etiology.

Evaluation of dexmedetomidine anesthesia-related temperature changes: preliminary retrospective observational study

“…Temperature ≥ 37.8 °C was adopted to define acceptable limit for fever, while 34.6 °C was the temperature that induced thermoregulatory response of peripheral vasoconstriction in normal individuals exposed to cooling. 9 , 23 …”

Microbial and Host Metabolites at the Backstage of Fever: Current Knowledge about the Co-Ordinate Action of Receptors and Molecules Underlying Pathophysiology and Clinical Implications

“…Moreover, these syndromes are characterized by the absence of an identified cause of fever, despite several investigations, and the persistence of fever for enough time to rule out self-limiting fevers [ 93 ]. According to Haidar and Singh, FUO is not a uniform biological event but a common expression of multiple and different clinical conditions, which may vary according to the immune status of the host, patient hospitalization, and travel history [ 94 ]. Consequentially, there is no general agreement on time cutoff or diagnostic criteria for FUO.…”

“…Other categories of FUO and IUO are represented by nosocomial fever, fever associated to immunodeficiency and immunosuppressive therapy and FUO in returning travellers [ 94 ]. With special reference to immunodeficiency and FUO, millions of people in the United States receive immunosuppressive drugs [monoclonal antibodies, checkpoint inhibitors, and chimeric antigen receptor (CAR) modified T-cells] [ 98 ].…”