Pyrexia of unknown origin Flashcards
Define fever
- elevation of body temp above normal (37 degrees)
- variation of up to 0.8 degrees daily (circadian rhythm): low in morning high in evening
- part of SIRS
Define pyrogens
Substances causing fever
- endogenous eg cytokines
- exogenous eg endotoxins from Gram -ve bacteria
- act at hypothalamic thermoregulatory centre to cause reduced heat loss and hence fever
Petersdorf and Beeson diagnosis of fever? (from 1961)
- temp >38.3 degrees
- recorded on multiple occasions
- present for at least 3 wks
- defied diagnosis after 1w hospital evaluation
Modern diagnosis of fever? (much broader than P+B definition)
- 3 outpatient visits or
- 3 days in hospital or
- 1w of outpatient investigation
What are the different variations of pyrexia of unknown origin (PUO)?
- Classical PUO
- Nosocomial PUO (develops in hospital, undiagnosed after 3 days)
- Neutropenic PUO (undiagnosed fever in patient with neutrophils <500/mm3)
- HIV associated PUO (fever in patient with HIV - present and undiagnosed for >3d in inpatient or 4 wks in outpatient)
What are the most common causes of HIV associated PUO?
- Mycobacterium tuberculosis
- Mycobacterium avium
- unknown
- more than 1 causative disease
Is it common for classical PUO to be undiagnosed? what percentage of cases goes undiagnosed?
yes - around 25%
Give some examples of infections causing PUO?
- TB
- HIV
- Endocarditis
- Pneumonia
Give examples of malignancy causing PUO?
- lymphoma
- metastatic disease
- renal cancer
Give examples of inflammatory diseases causing PUO?
- GCA
- IBD
- SLE
- Vasculitis
Other non-specific causes of PUO include…
- Drug fevers
- venous thrombosis
- sarcoidosis
In a patient history what is important to cover?
- travel
- occupation and hobbies (allergen exposure)
- FH and age onset - familial fevers eg TNF receptor associated periodic syndrome - TRAPS
- PMH and surgical history
- DH
In examining patient what should you be sure to cover?
skin, eyes, oral cavity, nails and LN. Repeating exam often worthwhile
What are initial investigations of PUO?
- CXR
- urinalysis and urine microscopy
- FBC and differential WCC
- CRP and ESR
- Blood cultures
- Urea, creatinine, electrolytes, LFTs
If the following indications are found:
- tropical travel
- new murmur
- headaches
- micro haematuria
- TB contact
- drug misuse
What further investigations should be made?
> Tropical: Blood for malarial parasites. Unlikely to be dengue if >21 days since return. HIV, bone marrow for leishmaniasis
Murmur: Echo (trans-oesophageal)
Headaches: TA biopsy or CT PET
Micro-haematuria: auto-antib., renal biopsy (polyarteritis) USS (renal Ca)
TB: sputum smear, bone marrow, mantoux test
drug misuse: screen for blood borne viruses
