FEVER OF UNKNOWN ORIGIN

23 FEVER OF UNKNOWN ORIGIN



General Discussion


Fever of unknown origin (FUO) is defined as a temperature elevation of 101°F (38.3 °C) or higher for 3 weeks or longer, the cause of which is not diagnosed after 1 week of intensive in-hospital investigation. Some attempts have been made to change the definition of FUO in special populations, such as “classic FUO,” “nosocomial FUO,” “FUO in neutropenic patients,” and “FUO in HIV patients.” Although such categorization has its merits, the pathogens in each of these categories merely reflect the frequency distribution of diseases causing prolonged fevers in these categories. Such categorization does not significantly alter or improve the diagnostic approach.


Recent series show that the diseases responsible for FUO involve over 100 disorders. The differential diagnosis of FUO can be divided into four subgroups: infections, malignancies, autoimmune conditions, and miscellaneous. Traditionally, infectious diseases represent the largest group of illnesses causing FUOs. However, the incidence of malignancy responsible for FUO has increased and in some published series is the most common cause of FUOs. As the duration of the fever increases, the likelihood of an infectious etiology decreases.


Abdominal abscesses, tuberculosis, and endocarditis are the most common infectious causes of FUO. Hodgkin’s and non-Hodgkin’s lymphoma are the most common neoplastic diseases responsible for FUO. Adult Still’s disease and temporal arteritis are the most common autoimmune causes of FUO.


Atypical presentation of infection is common in older adults, particularly the very old (80+ years). Normal body temperature and the amplitude of circadian rhythm are reduced in frail elderly individuals, but not necessarily in healthy older persons. Twenty to thirty percent of elderly individuals with serious infections present with an absent or blunted fever response. Connective tissue diseases are identified as the cause of the illness with a relatively high frequency in patients older than 65 years. This is primarily because temporal arteritis and polymyalgia rheumatica are common in this age group.


Fever may be the sole or the most prominent feature of an adverse drug reaction.


Rash or eosinophilia may occur, though neither is common. Drug fever is a diagnosis of exclusion and may be confirmed by withdrawal of the offending medication.


Historical clues and physical findings, if present, provide the most useful diagnostic information in the evaluation of FUO. Repeated requestioning and re-examination over time is extremely important as findings that were not initially apparent may become so and provide important clues to the diagnosis. Testing should be guided by the history and physical examination. It is not cost effective to order batteries of screening tests without some clinical suspicion for a diagnosis. The diagnostic objective is to use the history, physical examination, and laboratory data to establish a pattern of organ involvement.


Between 7 and 30% of FUO cases remain undiagnosed after thorough evaluation. However, fever resolves in the majority of these patients within a short time, and the mortality rate is 3% 5 years later. Only rarely did a serious disorder emerge later.



Medications Associated with FUO



Allopurinol

Aminoglycosides

Amphotericin

Atropine

Captopril

Cephalosporins

Cimetidine

Clindamycin

Clofibrate

Erythromycin

Heparin

Hydralazine

Hydrochlorothiazide

Interferon

Interleukin-2

Isoniazid

Macrolides

Meperidine

Methyldopa

Nifedipine

Nitrofurantoin

Penicillins

Phenytoin

Procainamide

Quinidine

Rifampin

Sulfonamides

Vancomycin


Causes of FUO



Infections
• Abdominal abscesses

• Amebiasis

• Blastomycosis

• Brucellosis

• Cat-scratch disease

• Coccidioidomycosis

• Colorado tick fever

• Complicated urinary tract infection

• Cytomegalovirus mononucleosis

• Dengue

• Dental abscesses

• Encephalitis

• Endocarditis

• Epstein–Barr virus

• Filariasis

• Histoplasmosis

• Human immunodeficiency virus

• Leptospirosis

• Lyme disease

• Lymphocytic choriomeningitis

• Malaria

• Meningitis (chronic)

• Mycobacterium avium–intracellulare complex

Related posts:

  1. ARTHRITIS AND ARTHRALGIA
  2. GYNECOMASTIA
  3. INFERTILITY, MALE
  4. SYNCOPE

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Aug 17, 2016 | Posted by in PEDIATRICS | Comments Off on FEVER OF UNKNOWN ORIGIN

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