A. Fever without localizing symptoms, rash or lymphadenopathy
ii. Those with fever beyond 3 weeks (FUO)
Definition: Fever of unknown origin (FUO) is a term applied to a febrile illness with temperatures exceeding >101?F (38.3?C) that is at least 3 weeks' duration and remains undiagnosed after 3 days in the hospital or after 3 outpatient visits. This is further categorized into:
1. Neutropenic (neutrophils </= 500): check for perianal, periodontal infections and candidemia, aspergillosis.
3. Nosocomial FUO: septic thrombophlebitis, clostridium difficile colitis and drug fever.
a. Infections: account for 1/3 of the causes.
Abscesses account for 1/3 of the causes. Most of these are intra-abdominal as abscesses, abscesses elsewhere are easily diagnosed.
Lower urinary tract infections.
Endovascular infections: infective endocarditis, mycotic aneurysms, infected atherosclerotic plaques.
c. Collagen vascular diseases: account for 10%. SLE is an uncommon cause as it is readily diagnosed serologically.
d. Granulomatous disease without defined etiology (e.g. sarcoidosis).
1. Thermometer in the tea cup routine.
2. Self-injection with pyrogenic containing substances.
3. Injection of medication known by the patient to cause fever.
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