Pyrexia of Unknown Origin

Question 1

what is fever?

Answer 1

any elevation of body temperature above the normal

Question 2

describe circadian rhythm of body temperature

Answer 2

varies up to 0.8 C
low in early morning
high 4-6pm

Question 3

what is the name for the substance which cause fever?

Answer 3

pyrogens

Question 4

where to pyrogens come from?

Answer 4

exogenous - e.g. endotoxins of gram neg bacteria

endogenous - cytokine

Question 5

how to pyrogens work?

Answer 5

cause elevation of set point of the hypothalamic thermoregulatory centre which causes vasoconstriction, decreased peripheral heat loss

Question 6

define pyrexia of unknown origin

Answer 6

no diagnosis after 3 outpatient visits, or 3 days in hospital or one week of outpatient investifation

Question 7

name 3 forms of PUO

Answer 7

nosocomial
neutropenic
HIV associated

Question 8

what is nosocomial PUO?

Answer 8

fever which develops in hospital and is undiagnosed after 3 days of investigation including two days of cultures

Question 9

what is neutropenic PUO?

Answer 9

fever in a patient with a neutrophil count of < 500 cells/mm3 which is undiagnosed after 3 days of investifation

Question 10

what is HIV-associated PUO?

Answer 10

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

Question 11

what may cause HIV associated PUO?

Answer 11

mycobacterium tuberculosis
mycobacterium avium
often more than one causative disease

Question 12

what are the important parts of a Hx in a patient with PUO?

Answer 12

travel
occupation
drug and sexual history
chemical exposure
surgical procedures
familial disorders
patter of fever
rashes

Question 13

why seek extensive imaging in the investigation of PUO?

Answer 13

enable diagnosis

exclude serious sepsis or malignancy

Question 14

CT scans can help identify small abnormalities. why may none be seen?

Answer 14

take time to develop

may not develop normally in an immunocompomised patient

Question 15

isotope bone scans may help identify what?

Answer 15

bone and joint infections

Question 16

V/Q scans may help assess patients with suspected what?

Answer 16

multiple PE

Question 17

invasive investigations in PUO

Answer 17

tissue for culture and histology
bone marrow exam
liver biopsy 
laparoscopy
lung/lymph node/renal biopsy if clinically indicated

Question 18

define factitious fever

Answer 18

patient has manipulated temperature recordings to fabricate the existence of a fever

Question 19

features of a patient with factitious fever

Answer 19

normal pulse with no elevation of inflammatory markers such as CRP despite being “febrile”

Question 20

define fabricated fever

Answer 20

these fevers are genuinely present but has developed as a consequence of self-induced infection

Question 21

what is a common cause of fabricated fever?

Answer 21

self-injection with faeces

Question 22

who should you consult before speaking to a patient with fabricated fever?

Answer 22

psychiatrist

Question 23

management of a patient with PUO if they are clearly unwell and without diadnosis

Answer 23

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.

Question 24

initial investigations in a patient with PUO

Answer 24

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

Question 25

examples of clinical indications prompting further investigation: travel to tropical areas

Answer 25

repeated blood films for malarial parasites
blood films for borrelia (Relapsing fevers) and trypano-somiasis, rikettsial, coxiela, dengue, schistosoma, filarial and amoebic serology

Question 26

examples of clinical indications prompting further investigation: new/changing heart murmur

Answer 26

echo

trans-oesophageal echo may be needed toreaveal small aortic valve vegetations

Question 27

examples of clinical indications prompting further investigation: headaches, jaw caludication

Answer 27

temporal artery biopsy

Question 28

examples of clinical indications prompting further investigation: microscopic haematuria

Answer 28

ANCA - vasculitis

renal USS - renal cell renal impairment carcinoma

Question 29

examples of clinical indications prompting further investigation: risk of TB (contact Hx, travel, past TB)

Answer 29

culture of sputum
early morning urine
bone marrow and liver biopsies

Question 30

examples of clinical indications prompting further investigation: injection drug misuse, high risk sexual contacts

Answer 30

HIV antibody

hep B+C serology