Fever of Unknown Origin

Question 1

FUO definition

Answer 1

a temperature >101/38.3 for longer than 3 weeks

3 outpatient visits or 3 days in the hospital or 1 week of “intelligent and invasive” ambulatory investigation

Question 2

FUOs are usually

Answer 2

unusual presentations of common diseases
or
common presentations of less common diseases

rarely are “Rare” diseases

Question 3

usually fever =

Answer 3

inflammation

Question 4

endogenous pyrogens vs exogenous pyrogens

Answer 4

Endogenous pyrogens – Interleukins (1, 6); TNF, IFNs; triggered by many pathways (infection, cancer, immune diseases) – remember these Big Three Categories

Exogenous pyrogens (produced outside the body) – most related to infection: microbial toxins, products of microbial origin, (e.g., endotoxin)

Question 5

FUO is a ___ ____ ____

Answer 5

systemic inflammatory syndrome

Question 6

Petersdorf’s main cause of unexplained febrile illnesses was

Answer 6

infections

Question 7

petersdorf did not stress that _____

Answer 7

many etiologies cross categories and overlap

infectious vs immune vs malignancy

Question 8

the ____ of symptoms is critical

Answer 8

duration
infectious are rapid but there are exceptions with chronic inflammation
malignancies declare within weeks
rheumatologic/immune have long histories that wax and wane, months to yrs

Question 9

key FUO questions

Answer 9

Duration of Fever + series of episodes or one continuous episode?

Temporal Pattern of Fever – periodicity (hours, days; are there near normal intervals between)

• Is the patient ill-appearing? (THIS IS THE MOST IMPORTANT QUALIFYER)
• –Acutely ill – distress, “toxic” (unstable vital signs)
• –Weight loss
• –Other findings on ROS and exam