Fever
Fever of unknown origin (FUO) is a medical term used to describe a persistent fever for which the cause cannot be determined despite extensive diagnostic evaluation. It is typically defined as a fever persisting for more than three weeks with temperatures higher than 38.3°C (100.9°F) on several occasions, along with no obvious diagnosis after one week of inpatient evaluation or three outpatient visits.
FUO can be classified into several categories:
- Classic FUO: This refers to a fever that persists for more than three weeks without an evident cause despite thorough evaluation.
- Nosocomial FUO: A fever that develops in hospitalized patients and cannot be attributed to a specific infection or medical condition.
- HIV-associated FUO: Patients with HIV infection may develop prolonged fever due to opportunistic infections, malignancies, or other HIV-related complications.
- Neutropenic FUO: Febrile episodes in patients with neutropenia (low white blood cell count) who are at increased risk of infections due to their compromised immune system.
Identifying the cause of FUO can be challenging and often requires a systematic and comprehensive approach, including:
- Detailed medical history: Identifying potential exposure to infectious agents, travel history, occupational exposures, medication history, and other relevant factors.
- Physical examination: Identifying any clues or signs that may suggest a specific underlying condition.
- Laboratory tests: Blood tests, urine tests, cultures, serological tests, and other diagnostic investigations to detect infections, autoimmune diseases, malignancies, and other potential causes of fever.
- Imaging studies: X-rays, ultrasound, CT scans, MRI scans, or other imaging modalities may be used to detect abnormalities in various organs or tissues.
- Specialized tests: Depending on the suspected underlying cause, additional tests such as biopsies, lumbar puncture, or specific antibody tests may be warranted.
The approach to managing FUO involves collaboration among various medical specialists, including infectious disease specialists, rheumatologists, oncologists, and others, depending on the suspected etiology. Treatment is directed toward addressing the underlying cause, if identified, and may include antimicrobial therapy for infections, immunosuppressive agents for autoimmune diseases, or chemotherapy for malignancies.
In some cases, despite extensive evaluation, the cause of FUO may remain elusive. Management in such cases focuses on controlling symptoms and supportive care. Regular follow-up and re-evaluation may be necessary to monitor for any changes or new developments that could provide further clues to the underlying cause of fever.
