5-Minute Clinical Consult
Fever of Unknown Origin (FUO)
Fever of Unknown Origin (FUO) is a topic covered in the 5-Minute Clinical Consult.
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Basics
Description
- Classic definition
- Repeated fever >38.3°C
- Fever duration at least 3 weeks
- Diagnosis remains uncertain after 1 week of study in the hospital.
- The definition of fever of unknown origin (FUO) has evolved and is based on patient characteristics and presentation. The need for in-hospital evaluation has been eliminated in previously healthy people.
- Some expand the definition to include nosocomial, neutropenic (immunodeficient), and HIV-associated fevers.
Epidemiology
Incidence
The exact incidence is not known
Etiology and Pathophysiology
- >200 causes; each with prevalence of ≤5%
- Most commonly, FUO is an atypical presentation of a common condition.
- Spectrum of causes varies widely.
- Noninfectious inflammatory diseases are the most frequent causes in high-income countries. Common causes include temporal arteritis, polymyalgia rheumatica, or rheumatoid arthritis.
- Infection
- Abdominal or pelvic abscesses
- Amebic hepatitis
- Catheter infections
- Cytomegalovirus
- Dental abscesses
- Endocarditis/pericarditis
- HIV (advanced stage)
- Mycobacterial infection (often with advanced HIV)
- Osteomyelitis
- Pyelonephritis or renal abscess
- Sinusitis
- Wound infections
- Other miscellaneous infections
- Neoplasms
- Atrial myxoma
- Colorectal cancer and other GI malignancies
- Hepatoma
- Lymphoma
- Leukemia
- Solid tumors (renal cell carcinoma)
- Noninfectious inflammatory disease
- Connective tissue diseases
- Adult Still disease
- Rheumatoid arthritis
- Systemic lupus erythematosus
- Granulomatous disease
- Crohn disease
- Sarcoidosis
- Vasculitis syndromes
- Giant cell arteritis
- Polymyalgia rheumatica
- Connective tissue diseases
- Other causes
- Alcoholic hepatitis
- Cerebrovascular accident
- Cirrhosis
- Medications
- Allopurinol, captopril, carbamazepine, cephalosporins, cimetidine, clofibrate, erythromycin, heparin, hydralazine, hydrochlorothiazide, isoniazid, meperidine, methyldopa, nifedipine, nitrofurantoin, penicillin, phenytoin, procainamide, quinidine, sulfonamides
- Endocrine disease
- Factitious/fraudulent fever
- Occupational causes
- Periodic fever
- Pulmonary emboli/deep vein thrombosis
- Thermoregulatory disorders
- In up to 20–30% of cases, the cause of the fever is never identified despite a thorough workup.
Risk Factors
- Recent travel (malaria, enteric fevers)
- Exposure to biologic or chemical agents
- HIV infection (particularly in acute infection and advanced stages)
- Elderly
- Drug abuse
- Immigrants
- Young, (typically) female health care workers (factitious fever)
Geriatric Considerations
Common infectious causes of FUO in geriatric populations include intra-abdominal abscess, urinary tract infection, tuberculosis (TB), and endocarditis. Other common causes of FUO in patients >65 years include malignancies (particularly hematologic cancers) and drug-induced fever.
Pediatric Considerations
- ~50% of FUO in pediatric cases are infectious. Collagen vascular disease and malignancy are the next most common.
- Inflammatory bowel disease is a common cause of FUO in older children and adolescents.
-- To view the remaining sections of this topic, please sign in or purchase a subscription --
Basics
Description
- Classic definition
- Repeated fever >38.3°C
- Fever duration at least 3 weeks
- Diagnosis remains uncertain after 1 week of study in the hospital.
- The definition of fever of unknown origin (FUO) has evolved and is based on patient characteristics and presentation. The need for in-hospital evaluation has been eliminated in previously healthy people.
- Some expand the definition to include nosocomial, neutropenic (immunodeficient), and HIV-associated fevers.
Epidemiology
Incidence
The exact incidence is not known
Etiology and Pathophysiology
- >200 causes; each with prevalence of ≤5%
- Most commonly, FUO is an atypical presentation of a common condition.
- Spectrum of causes varies widely.
- Noninfectious inflammatory diseases are the most frequent causes in high-income countries. Common causes include temporal arteritis, polymyalgia rheumatica, or rheumatoid arthritis.
- Infection
- Abdominal or pelvic abscesses
- Amebic hepatitis
- Catheter infections
- Cytomegalovirus
- Dental abscesses
- Endocarditis/pericarditis
- HIV (advanced stage)
- Mycobacterial infection (often with advanced HIV)
- Osteomyelitis
- Pyelonephritis or renal abscess
- Sinusitis
- Wound infections
- Other miscellaneous infections
- Neoplasms
- Atrial myxoma
- Colorectal cancer and other GI malignancies
- Hepatoma
- Lymphoma
- Leukemia
- Solid tumors (renal cell carcinoma)
- Noninfectious inflammatory disease
- Connective tissue diseases
- Adult Still disease
- Rheumatoid arthritis
- Systemic lupus erythematosus
- Granulomatous disease
- Crohn disease
- Sarcoidosis
- Vasculitis syndromes
- Giant cell arteritis
- Polymyalgia rheumatica
- Connective tissue diseases
- Other causes
- Alcoholic hepatitis
- Cerebrovascular accident
- Cirrhosis
- Medications
- Allopurinol, captopril, carbamazepine, cephalosporins, cimetidine, clofibrate, erythromycin, heparin, hydralazine, hydrochlorothiazide, isoniazid, meperidine, methyldopa, nifedipine, nitrofurantoin, penicillin, phenytoin, procainamide, quinidine, sulfonamides
- Endocrine disease
- Factitious/fraudulent fever
- Occupational causes
- Periodic fever
- Pulmonary emboli/deep vein thrombosis
- Thermoregulatory disorders
- In up to 20–30% of cases, the cause of the fever is never identified despite a thorough workup.
Risk Factors
- Recent travel (malaria, enteric fevers)
- Exposure to biologic or chemical agents
- HIV infection (particularly in acute infection and advanced stages)
- Elderly
- Drug abuse
- Immigrants
- Young, (typically) female health care workers (factitious fever)
Geriatric Considerations
Common infectious causes of FUO in geriatric populations include intra-abdominal abscess, urinary tract infection, tuberculosis (TB), and endocarditis. Other common causes of FUO in patients >65 years include malignancies (particularly hematologic cancers) and drug-induced fever.
Pediatric Considerations
- ~50% of FUO in pediatric cases are infectious. Collagen vascular disease and malignancy are the next most common.
- Inflammatory bowel disease is a common cause of FUO in older children and adolescents.
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Citation
Stephens, Mark B., et al., editors. "Fever of Unknown Origin (FUO)." 5-Minute Clinical Consult, 27th ed., Wolters Kluwer, 2020. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/816017/all/Fever_of_Unknown_Origin__FUO_.
Fever of Unknown Origin (FUO). In: Stephens MB, Golding J, Baldor RA, et al, eds. 5-Minute Clinical Consult. Wolters Kluwer; 2020. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/816017/all/Fever_of_Unknown_Origin__FUO_. Accessed September 19, 2020.
Fever of Unknown Origin (FUO). (2020). In Stephens, M. B., Golding, J., Baldor, R. A., & Domino, F. J. (Eds.), 5-Minute Clinical Consult (27th edition). Wolters Kluwer. Retrieved September 19, 2020, from https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/816017/all/Fever_of_Unknown_Origin__FUO_
Fever of Unknown Origin (FUO) [Internet]. In: Stephens MB, Golding J, Baldor RA, Domino FJ, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2020. [cited 2020 September 19]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/816017/all/Fever_of_Unknown_Origin__FUO_.
* Article titles in AMA citation format should be in sentence-case
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T1 - Fever of Unknown Origin (FUO)
ID - 816017
ED - Stephens,Mark B,
ED - Golding,Jeremy,
ED - Baldor,Robert A,
ED - Domino,Frank J,
BT - 5-Minute Clinical Consult, Updating
UR - https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/816017/all/Fever_of_Unknown_Origin__FUO_
PB - Wolters Kluwer
ET - 27
DB - Medicine Central
DP - Unbound Medicine
ER -
