Pyrexia of Unknown Origin Flashcards
what is fever?
any elevation of body temperature above the normal
describe circadian rhythm of body temperature
varies up to 0.8 C
low in early morning
high 4-6pm
what is the name for the substance which cause fever?
pyrogens
where to pyrogens come from?
exogenous - e.g. endotoxins of gram neg bacteria
endogenous - cytokine
how to pyrogens work?
cause elevation of set point of the hypothalamic thermoregulatory centre which causes vasoconstriction, decreased peripheral heat loss
define pyrexia of unknown origin
no diagnosis after 3 outpatient visits, or 3 days in hospital or one week of outpatient investifation
name 3 forms of PUO
nosocomial
neutropenic
HIV associated
what is nosocomial PUO?
fever which develops in hospital and is undiagnosed after 3 days of investigation including two days of cultures
what is neutropenic PUO?
fever in a patient with a neutrophil count of < 500 cells/mm3 which is undiagnosed after 3 days of investifation
what is HIV-associated PUO?
fever in a patient with HIV which has been present and undiagnosed for more than 3 days as in inpatient or 4 weeks as an outpatient
what may cause HIV associated PUO?
mycobacterium tuberculosis
mycobacterium avium
often more than one causative disease
what are the important parts of a Hx in a patient with PUO?
travel occupation drug and sexual history chemical exposure surgical procedures familial disorders patter of fever rashes
why seek extensive imaging in the investigation of PUO?
enable diagnosis
exclude serious sepsis or malignancy
CT scans can help identify small abnormalities. why may none be seen?
take time to develop
may not develop normally in an immunocompomised patient
isotope bone scans may help identify what?
bone and joint infections
V/Q scans may help assess patients with suspected what?
multiple PE
invasive investigations in PUO
tissue for culture and histology bone marrow exam liver biopsy laparoscopy lung/lymph node/renal biopsy if clinically indicated
define factitious fever
patient has manipulated temperature recordings to fabricate the existence of a fever
features of a patient with factitious fever
normal pulse with no elevation of inflammatory markers such as CRP despite being “febrile”
define fabricated fever
these fevers are genuinely present but has developed as a consequence of self-induced infection
what is a common cause of fabricated fever?
self-injection with faeces
who should you consult before speaking to a patient with fabricated fever?
psychiatrist
management of a patient with PUO if they are clearly unwell and without diadnosis
trail of antituberculous therapy or
steroids should be considered. For patients with suspected tuberculosis the diagnosis becomes likely
if there is a response within one week of starting anti-tuberculous therapy. Steroids will often improve
a fever as well as patient well-being but the response to steroids in patients with giant cell arteritis or
Still’s disease is dramatic and should be seen after 24-72 hours.
initial investigations in a patient with PUO
CXR Urinalysis and urine microscopy FBC and differential WCC CRP and erythrocyte sedimentation rate Blood cultures taken at times of fevers Urea, creatinine, electrolytes, LFTs
examples of clinical indications prompting further investigation: travel to tropical areas
repeated blood films for malarial parasites
blood films for borrelia (Relapsing fevers) and trypano-somiasis, rikettsial, coxiela, dengue, schistosoma, filarial and amoebic serology
examples of clinical indications prompting further investigation: new/changing heart murmur
echo
trans-oesophageal echo may be needed toreaveal small aortic valve vegetations
examples of clinical indications prompting further investigation: headaches, jaw caludication
temporal artery biopsy
examples of clinical indications prompting further investigation: microscopic haematuria
ANCA - vasculitis
renal USS - renal cell renal impairment carcinoma
examples of clinical indications prompting further investigation: risk of TB (contact Hx, travel, past TB)
culture of sputum
early morning urine
bone marrow and liver biopsies
examples of clinical indications prompting further investigation: injection drug misuse, high risk sexual contacts
HIV antibody
hep B+C serology
