Fever of unknown origin pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Pathophysiology
Presently FUO cases are codified in four subclasses.
- Classic FUO
This refers to the original classification by Petersdorf and Beeson. The outpatient setting has been included to reflect current medical practise. The current definition requires three outpatient visits or three days in hospital or 1 week of "intelligent and invasive" ambulatory investigation.[1] Studies show there are five categories of conditions: infections (i.e. abscesses, endocarditis, tuberculosis, and complicated urinary tract infections), neoplasms (i.e. lymphomas, leukaemias), connective tissue diseases (i.e. temporal arteritis and polymyalgia rheumatica, Still's disease, systemic lupus erythematosus, and rheumatoid arthritis), miscellaneous disorders (i.e. alcoholic hepatitis, granulomatous conditions), and undiagnosed conditions.[2][3]
The new definition is broader, stipulating three outpatient visits or 3 days in the hospital without elucidation of a cause or 1 week of "intelligent and invasive" ambulatory investigation.
- Nosocomial FUO
Nosocomial FUO refers to pyrexia in patients that have been admitted to hospital for at least 24 hours. This is commonly related to hospital associated factors such as, surgery, use of urinary catheter, intravascular devices (i.e. "drip", pulmonary artery catheter), drugs (antibiotics induced Clostridium difficile colitis, and drug fever), immobilization (decubitus, thromboembolic event). Sinusitis in the intensive care unit is associated with nasogastric and orotracheal tubes.[2][1][3] Other conditions that should be considered are deep-vein thrombophlebitis, and pulmonary embolism, transfusion reactions, acalculous cholecystitis, thyroiditis, alcohol/drug withdrawal, adrenal insufficiency, pancreatitis.[1]
- Immune-deficient FUO
Immunodeficiency can be seen in patients receiving chemotherapy or in hematologic malignant neoplasms. Fever is concommittent with neutropenia (neutrophil <500/uL) or impaired cell-mediated immunity. The lack of immune response masks a potentially dangerous course. Infection is the most common cause.[2][1][3]
- Human immunodeficiency virus (HIV)-associated FUO
HIV-infected patients are a subgroup of the immunodeficient FUO, and frequently have fever. The primary phase shows fever since it has a mononucleosis-like illness. In advanced stages of infection fever mostly is the result of a superimposed illness.[2][1][3]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 Harrison's Principles of Internal Medicine 16th Edition, The McGraw-Hill Companies, ISBN 0-07-140235-7
- ↑ 2.0 2.1 2.2 2.3
- ↑ 3.0 3.1 3.2 3.3 The Oxford Textbook of Medicine Edited by David A. Warrell, Timothy M. Cox and John D. Firth with Edward J. Benz, Fourth Edition (2003), Oxford University Press, ISBN 0-19-262922-0