Pyrexia of Unknown Origin Flashcards
Define fever
Elevation of body temperature above normal (37C)
Part of SIRS
What is normal body temperature?
37C
But fluctuation of 0.8C during the normal circadian rhythm (lowest in the morning, highest at night)
What are pyrogens?
Substances which cause fever
How do pyrogens work?
Act on the hypothalamic thermoregulatory centre to cause reduced heat loss in the body –> fever
Give examples of pyrogens
Exogenous pyrogens include endotoxins from gram -ve bacteria (LPS)
Endogenous pyrogens include cytokines
Define pyrexia of unknown origin
3 outpatient visits
3 days in hospital
OR
1 week of outpatient investigation for a fever without diagnosis
What are the 4 types of PUO?
Classic
Nosocomial
Neutropenic
HIV-associated
What is classic PUO?
Follows original definition of PUO
What are the five categories of classic PUO?
Infection (e.g. TB, endocarditis, abscesses)
Malignancy (e.g. leukaemia)
Connective tissue dx (e.g. temporal arteritis/RA)
Miscellaneous (e.g. alcoholic hepatitis)
Undiagnosed (most common)
What is nosocomial PUO?
Fever that develops in hospital and is undiagnosed after 3 days
What is neutropenic PUO?
Undiagnosed fever in a patient with neutrophils <500/mm3
What is HIV-associated PUO?
Undiagnosed fever occurring in an HIV patient which is present and undiagnosed for more than 3 days as an impatient, or four week as an outpatient
What is the most common cause for HIV-associated PUO?
Mycobacterium tuberculosis (then mycobacterium avium)
Common for multiple causative agents/unknown
How do you assess a patient with PUO?
History, examination, investigations and imaging if necessary
What are the key things to ask in your history of a patient with PUO?
Hx of travel, occupation, hobbies, drug history, PMH, FG, pattern of fever
What are key things to include in your examination of a patient with PUO?
Check skin, eyes, oral cavity, nails, lymph nodes
May be worthwhile repeating!
What investigations may you carry out in someone with PUO?
CXR, urinalysis, urine microscopy, FBC, differential WCC, ESR, CRP, blood culture (from time of fever), urea, creatinine, electrolytes, LFTs
When might imaging be valuable?
What imaging might you do?
If you have some direction
E.g.s - CT, USS, MRI, PET with FDG marker
If a patient presents with PUO & hx of tropical travel, what investigations may be useful?
Blood for malarial parasite, dengue, HIV testing, bone marrow testing for leishmaniasis
Less likely if >21 days since return
If a patient presents with PUO & a new murmur, what investigations may be useful?
Echocardiogram
If a patient presents with PUO & new headache, what investigations may be useful?
Temporal artery biopsy
If a patient presents with PUO & microhaematuria, what investigations may be useful?
Auto-antibodies +/- renal biopsy (polyarteritis), USS (renal Ca)
If a patient presents with PUO & hx contact with TB, what investigations may be useful?
Sputum smear, bone marrow testing, Mantoux test
If a patient presents with PUO & hx of drug misuse, what investigations may be useful?
Screen for blood borne viruses
When might you do a therapeutic trial in someone with PUO?
Anti-TB therapy if suspected TB (diagnosis of TB unlikely if no response to treatment within 2 weeks)
Steroids for suspected vasculitis/connective tissue disease - expect dramatic response (usually within 24h), esp with temporal arteritis
What might be a clue that a patient’s fever is fabricated?
Patient often continues despite being quite sick
What should you do in the case of a fabricated fever?
Seek psychiatric help as opposed to confronting the patient
Some patients with no diagnosis response to which two drugs?
Steroids or NSAIDs
