FUO is body temperature ≥ 38.3° C (101° F) rectally that does not result from transient and self-limited illness, rapidly fatal illness, or disorders with clear-cut localizing symptoms or signs or with abnormalities on common tests such as chest x-ray, urinalysis, or blood cultures.
| Category of FUO | Definition | Common etiologies |
| Classic | Temperature >38.3°C (100.9°F) Duration of >3 weeks Evaluation of at least 3 outpatient visits or 3 days in hospital |
Infection, malignancy, collagen vascular disease |
| Nosocomial | Temperature >38.3°C Patient hospitalized >=24 hours but no fever or incubating on admission Evaluation of at least 3 days |
Clostridium difficile enterocolitis, drug-induced, pulmonary embolism, septic thrombophlebitis, sinusitis |
| Immune deficient (neutropenic) | Temperature >38.3°C Neutrophil count <=500 per mm3 Evaluation of at least 3 days |
Opportunistic bacterial infections, aspergillosis, candidiasis, herpes virus |
| HIV-associated | Temperature >38.3°C Duration of >4 weeks for outpatients, >3 days for inpatients HIV infection confirmed |
Cytomegalovirus, Mycobacterium avium-intracellulare complex, Pneumocystis carinii pneumonia, drug-induced, Kaposi’s sarcoma, lymphoma |
HIV = human immunodeficiency virus.
Common Etiologies of Fever of Unknown Origin
Infections
- Tuberculosis (especially extrapulmonary)
- Abdominal abscesses
- Pelvic abscesses
- Dental abscesses
- Endocarditis
- Osteomyelitis
- Sinusitis
- Cytomegalovirus
- Epstein-Barr virus
- Human immunodeficiency virus
- Lyme disease
- Prostatitis
- Sinusitis
Malignancies
- Chronic leukaemia
- Lymphoma
- Metastatic cancers
- Renal cell carcinoma
- Colon carcinoma
- Hepatoma
- Myelodysplastic syndromes
- Pancreatic carcinoma
- Sarcomas
Autoimmune conditions
- Adult Still’s disease
- Polymyalgia rheumatica
- Temporal arteritis
- Rheumatoid arthritis
- Rheumatoid fever
- Inflammatory bowel disease
- Reiter’s syndrome
- Systemic lupus erythematosus
- Vasculitides
Miscellaneous
- Drug-induced fever
- Complications from cirrhosis
- Factitious fever
- Hepatitis (alcoholic, granulomatous, or lupoid)
- Deep venous thrombosis
- Sarcoidosis
References:
- Durack DT, Street AC. Fever of unknown origin–reexamined and redefined. Curr Clin Top Infect Dis. 1991;11:35-51. [Medline]
- Hirschmann JV. Fever of unknown origin in adults. Clin Infect Dis. 1997 Mar;24(3):291-300 [Medline]
Created: July 04, 2006
