Pyrexia of Unknown Origin Flashcards
What temperature is considered a fever or pyrexia?
> 38 celsius
What are pyrogens?
Substances that cause fever:
- Endogenous e.g. cytokines
-Exogenous e.g. endotoxins from G. neg. bacteria.
They act at the hypothalamic centre for thermoregulation
How do we define PUO?
Pyrexia that has had no diagnosis after 3 outpatient visits, 3 days in hospital or 1 week of outpatient investigation.
What are the different types of PUO?
Classical
Nosocomial (hospital acquired)
Neutropenic PUO (neutrophils<500/mm3)
HIV-associated
What are the common causes of HIV related PUO?
Often infectious:
- Mycobacterium tuberculosis
- Mycobacterium avium
Unknown
More than one causative disease/infection
What are the categories causing classical PUO?
Infection - TB/HIV/IE Neoplasm - Lymphoma/Mets/Renal carcinoma Inflammatory - Temporal arteritis/IBD/SLE/Vasculitis Miscellaneous - Drug fevers/sarcoid/DVT Undiagnosed
What are some important points to pick up on history of a PUO?
Travel
Occupation and hobbies (allergens)
Family history of periods of high fever (check genetics)
What investigations might you do to try to narrow down a PUO?
CXR Urinalysis/Culture FBC CRP and ESR Blood cultures U+E, Creatinine, LFTS
What specific things might you look for if indicated in PUO?
Malarial blood films, dengue, HIV, bone marrow for leishmaniasis Echocardiogram Temporal biopsy Autoantibodies and renal biopsy/US Mantoux test BB virus screen
When might you try a therapeutic trial in PUO?
TB or Vasculitis as they are hard to diagnose. Although this is raely used.
Usually TB will respond in 2 weeks and temporal arteritis will respond within 48 hours
When might we suspect a fabricated fever? (A form of Munchausen’s)
Evidence of self-injection, multiple different organisms at different times on blood culture.
Seek psychiatric advice.
What are the outcomes of PUO?
Most will have a spontaneous resolution - especially in young.
Some may respond to NSAIDs or steroids
