Fever and PUO

Question 1

What is pyrexia of unknown origin?

Answer 1

an illness of more than 2 to 3 weeks of duration with a fever and no diagnosis after intelligent investigations

Question 2

How much does temperature vary diurnally?

Answer 2

0.5 - 1 degree - highest in the afternoon

Question 3

Where is temperature regulated?

Answer 3

in the anterior hypothalamus

Question 4

How does the body lose heat?

Answer 4

peripheral vasodilation, sweating, and reduced physical activity

Question 5

How does the body conserve heat?

Answer 5

peripheral vasoconstriction, piloerection and warmth seeking behaviour

Question 6

How does the body produce heat?

Answer 6

shivering, release of thyroid hormones, glucocorticoids and catecholamines

Question 7

What oral temperature is defined as a fever?

Answer 7

> 37.8

Question 8

What ear temperature is defined as a fever?

Answer 8

> 38.0

Question 9

What is the purpose of a fever?

Answer 9

the increase in temperature switches on immune, endocrine and physiological mechanisms for fighting an infection

Question 10

What is the problem with having a fever for a long time?

Answer 10

it requires a lot of energy so will result in a breakdown of muscle and fat

Question 11

What is the mechanism of a fever?

Answer 11

bacterial and viral stimuli, Ag-Ab complexes and complement activates monocytes/macrophages and neutrophils and results in release of cytokines (IL-1, IL-6, IFNgamma and TNFalpha) which induces COX-2 to convert arachidonic acid to PGE2 which binds to thermoreceptors in the hypothalamus and stimulates shivering, rigors, vasoconstriction, piloerection, sweating and metabolic changes

Question 12

Which organisms can directly produce a fever?

Answer 12

gram negative bacteria with an endotoxin in the cell wall

Question 13

What is rigor?

Answer 13

a feeling of intense cold, uncontrollable shivering, pallor and piloerection - results in a high fever >39

Question 14

What are some causes of acute fever which are life threatening medical emergencies?

Answer 14

meningococcal septicaemia, falciparum malaria, bacterial meningitis, post splenectomy sepsis, toxic shock syndrome, necrotising soft tissue infections, head and neck space infections, febrile neutropenia, acute staph aureus endocarditis, severe pneumonia

Question 15

Which patients are more at risk of a life threatening acute fever?

Answer 15

recent OS travel, asplenic, neutropaenia, elderly, diabetic, IV drug users

Question 16

What is toxic shock syndrome?

Answer 16

where staph aureus or strep pyogenes acts as a super antigen and produces an overwhelming immune response resulting in a rash, hypotension, fever and chills

Question 17

What associated features make a fever seem more dangerous?

Answer 17

rapid onset, rigors, severe muscle pains, impaired conscious state, vomiting (marker of raised ICP), headache, rash, jaundice

Question 18

Why do you ask people with a prolonged fever about animal exposure?

Answer 18

because birds can transmit psitacossis which is an atypical pneumonia and Q fever can be transmitted by domestic mammals

Question 19

Why do you ask people with a prolonged fever about their country of origin?

Answer 19

TB

Question 20

Why do you ask people with a prolonged fever about travel from a few years ago?

Answer 20

because malaria vivax has a long dormant liver stage

Question 21

What infection are you worried about in a pregnant mother with a prolonged fever and a young toddler?

Answer 21

CMV

Question 22

What is the differential diagnosis for a PUO?

Answer 22

infection, connective tissue disorder, malignancy, drug fever, factitious, benign pyrexia

Question 23

What are the infectious causes of PUO?

Answer 23

subacute bacterial endocarditis, TB, intra abdominal abscess, HIV related opportunistic infection

Question 24

What are the connective tissue diseases associated with PUO?

Answer 24

polymyalgia rheumatica, temporal arteritis, vasculitis, adult still’s disease, SLE, acute thyroiditis, granulomatous diseases

Question 25

What malignancies may be assosciated with PUO?

Answer 25

lymphomas, leukemia, renal cell cancer, hepatoma, GI, atrial myxoma, mets in liver