Pyrexia of Unknown Origin Flashcards
Definition of fever
Elevation of body temperature above normal (37C)
Variation of fever
Variation of up to 0.8C daily (circadian rhythm)
- low in the morning
- high in the early evening
Definition of pyrogen
Substances which cause fever/raise your temperature
Types of pyrogens
Endogenous e.g. cytokines
Exogenous e.g. endotoxins from gram -ve bacteria
What do pyrogens do?
Act at hypothalamic thermoregulatory centre to cause reduced heat loss and hence fever
Criteria for SIRS
Pulse > 90
Temp < 35 or > 38
RR > 20
WCC >12 or <5
Criteria for pyrexia of unknown origin
Temp > 38C, recorded on multiple occasions, present for at least 3 weeks, defied diagnosis after 1 week of hospital evaluation OR No diagnosis after - 3 outpatient visits OR - 3 days in hospital OR - 1 week of outpatient investigations
Types of PUO
Classic PUO
Nosocomical PUO
Neutropenic PUO
HIV associated PUO
Definition of nosocomical PUO
Develops in hospital, undiagnosed after 3 days
Definition of neutropenic PUO
Undiagnosed fever in patient with neutrophils <500/mm3
Definition of HIV associated PUO
Fever in a patient with HIV infection - present and undiagnosed for > 3 days inpatient or 4 weeks outpatient
Causes of classical PUO
Infections - TB - HIV - Endocarditis Malignancy - Lymphoma - Metastatic disease - Renal carcinoma Inflammatory - temporal arteritis - IBD - SLE - vasculitis Other - drug fevers - venous thrombosis - Sarcoidosis
Definition of classic PUO
Undiagnosed fever presenting more than 3 days
Causes of HIV-associated PUO
Unknown 16%
More than 1 causative disease 20%
Mycobacterium tuberculosis 21%
Mycobacterium avium 18%
How much of PUO does HIV-associated PUO make up?
3/4 of patients
