Pyrexia of unknown origin Flashcards
fever
definition:
an abnormally high body temperature
exact measurement can vary - always >38C
OHCM says:
morning oral temperature >37.2
OR
an evening oral temp >37.7
causes of fever
daily spikes; abscess, TB, schistosomiasis
twice daily fever: leishmaniasis
saddleback fever (fever for 7 days then apyrexial for 3): dengue, legionnaire’s
longer periodicity: pel-ebstein (often seen in hodgkin’s lymphoma), cyclical fever with long periods (15-28 days) of normal or low temp
remitting: diurnal variation, not dipping to normal. e.g . kawasaki’s, malaria
fever pathology
endotoxins, inflammation or other pyrogenic stimuli act on macrophages, monocytes and kuppfer cells. these release cytokines which affect the preoptic area of the hypothalmus. prostaglandins are then released which raise the body’s temperature set point, reswulting in fever.
pyrogens effectively reset the body’s thermostat, making the body think it is cold. therefore attempts are made to conserve heat and/or warm up
pyrogens
a substance, typically produced by a bacterium, which produces fever if it gets into the blood
exogenous pyrogens come from outside the body
endogenous pyrogens include IL-1, IL-6 and TNF-alpha
endogenous pyrogens act as the mediator for the process
PUO
> 3weeks duration
fever ><38.3 on several occasions
unclear cause after 1 week of investigations
include specific categories with slightly different definitions: nosocomial, neutropenic, HIV-associated
causes of PUO
3 main categories:
infections
malignancies
connective tissue diseases (e.g. vasculitis, RA)
infections causing PUO
TB and abscess are the most common
abscess is usually abdominal or pelvic, ? underlying condition
others include: osteomyelitis, UTI, bacterial endocarditis
malignancies causing PUO
most common: lymphoma (especially NHL) leukaemia renal cell carcinoma hepatocellular carcinoma other cancers with liver mets
connective tissue disorders causing PUO
most common:
adults Still’s disease - young and middle aged adults, signs/Sx: daily fevers, arthritis and evanescent rash
giant cell arteritis - should be considered in those >50 with: headache abrupt loss of vision symptoms of polymyalgia rheumatica (PMR) unexplained fever/anaemia high ESR
adult still’s disease
rare type of arthritis similar to RA, beginning in adulthood
PMR
autoimmune inflammatory condition considered to be a form of vasculitis. causes pain and stiffness on the large muscles around the shoulders, hips and back
other causes of PUO
drugs (most common of the less common) disordered heat homeostasis dental abscess concurrent infections alcoholic hepatitis factitious fever
