Fever of Unknown Origin (FUO)

5-Minute Clinical Consult

Fever of Unknown Origin (FUO)

Fever of Unknown Origin (FUO) was found in 5-Minute Clinical Consult which helps you diagnose, treat, and follow up on over 900 medical conditions seen in everyday practice.

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Basics

Description

  • Classic definition by Petersdorf and Beeson:
    • Fever >38.3°C on several occasions
    • Fever duration at least 3 weeks
    • Uncertain diagnosis after 1 week of study in the hospital
  • Modifications to the definition have been proposed, including eliminating the in-hospital evaluation and shortening the exam time.
  • Some have suggested expansion of the definition to include nosocomial, neutropenic, and HIV-associated fevers that may not be prolonged.

Epidemiology

Incidence
No data on actual incidence

Risk Factors

  • Recent travel
  • Exposure to biologic or chemical agents
  • HIV-infected patients with advanced disease
  • Persons in AIDS risk group
  • Elderly
  • Drug abuse
  • Immigrants
  • Young female health care workers; consider factitious fever

Etiology

  • >200 causes; each with prevalence of ≤5%
  • Most commonly an atypical presentation of a common condition
  • Infection:
    • Abdominal abscesses
    • Amebic hepatitis
    • Catheter infections
    • Cytomegalovirus
    • Endocarditis/Pericarditis
    • HIV (advanced stage)
    • Mycobacterial infection (often with advanced HIV)
    • Osteomyelitis
    • Renal
    • Sinusitis
    • Wound infections
    • Other miscellaneous infections
  • Neoplasms:
    • Atrial myxoma
    • Colon cancer
    • Hepatoma
    • Lymphoma
    • Leukemia
    • Solid tumors (hypernephroma)
  • Collagen vascular disease:
    • Giant cell arteritis
    • Polyarteritis nodosa
    • Polymyalgia rheumatica
    • Systemic lupus erythematosus
    • Rheumatic fever
    • Rheumatoid arthritis
  • Other causes:
    • Alcoholic hepatitis
    • Cerebrovascular accident
    • Cirrhosis
    • Drug fever/medication induced:
      • Allopurinol, captopril, carbamazepine, cephalosporins, cimetidine, clofibrate, erythromycin, heparin, hydralazine, hydrochlorothiazide, isoniazid, meperidine, methyldopa, nifedipine, nitrofurantoin, penicillin, phenytoin, procainamide, quinidine, sulfonamides
    • Endocrinologic diseases
    • Factitious/fraudulent fever
    • Granulomatous diseases
    • Occupational causes
    • Periodic fever
    • Pulmonary emboli/deep vein thrombosis
    • Thermoregulatory disorders
  • In up to 20% of cases, the cause of the fever will not be identified despite thorough workup.
Geriatric Considerations
Most common causes are acute leukemia, Hodgkin lymphoma, intra-abdominal infections, tuberculosis (TB), and temporal arteritis.
  • Infections account for over half of causes, with collagen-vascular diseases the 2nd-most likely etiology.
Pediatric Considerations
  • ~50% of FUOs in published pediatric case series are ultimately shown to be due to infections; collagen vascular disease and malignancy also being common diagnoses (1)[A].
  • Inflammatory bowel disease is a common etiology in older children and adolescents.

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