Fever of Unknown Origin in Adults

Area of Science:

• Internal Medicine
• Diagnostic Medicine

Background:

• Fever of unknown origin (FUO) is defined by persistent high temperatures with an unrevealing diagnostic workup.
• The differential diagnosis for FUO is extensive, encompassing infections, malignancies, and inflammatory conditions.
• Many FUO cases in adults present as atypical forms of common diseases, with a significant percentage resolving without a specific diagnosis.

Purpose of the Study:

• To outline the diagnostic approach for fever of unknown origin.
• To highlight key investigations and interventions for identifying the cause of FUO.

Main Methods:

• Initiate workup with comprehensive history and physical examination to identify potential causes.
• Conduct initial laboratory testing for infectious, malignant, and inflammatory etiologies.
• Consider advanced imaging like 18F fluorodeoxyglucose positron emission tomography (FDG-PET) scans if initial evaluations are inconclusive and inflammatory markers are elevated.
• Proceed to tissue biopsy for definitive diagnosis when noninvasive methods fail.

Main Results:

• A systematic approach beginning with clinical evaluation is crucial for narrowing down FUO causes.
• Elevated erythrocyte sedimentation rate or C-reactive protein may warrant advanced imaging.
• Tissue biopsy offers a high diagnostic yield for persistent, undiagnosed fevers.
• Empiric antimicrobial therapy is generally not recommended for FUO, except in specific patient populations.

Conclusions:

• Effective management of FUO relies on a stepwise diagnostic strategy, starting with clinical assessment and progressing to targeted investigations.
• Advanced imaging and invasive procedures like biopsy are valuable tools when initial workup is unrevealing.
• Judicious use of empiric treatments is essential, reserving them for immunocompromised or critically ill patients.