Pyrexia of unknown origin

Question 1

What temperature is considered a fever?

Answer 1

Above 38 degrees Celsius

Question 2

What are the substances that cause the development of a fever called?

Answer 2

Pyrogens

Question 3

Give an example of an endogenous pyrogen

Answer 3

cytokine

Question 4

Give an example of an exogenous pyrogen

Answer 4

endotoxins from gram -ve bacteria

Question 5

What do pyrogens act on in the body?

Answer 5

The hypothalamic thermoregulatory centre causing reduced heat loss

Question 6

What are the 4 different types of pyrexia of unknown origin?

Answer 6

Classical

Nosocomial

Neutropenic

HIV-associated

Question 7

Nosocomial PUO

Answer 7

Develops in hospital, undiagnosed after 3 days might see this in compromised patients with HAI

Question 8

Neutropenic PUO

Answer 8

undiagnosed fever in patient with neutrophils <500/mm3

Classically seen in haematology patients who have a lower white cell count

Question 9

What are the 5 main causes of a classical PUO?

Answer 9

Infections

Tumour disease

Inflammatory conditions

Collagen and vascular diseases

Undiagnosed – ¼ of all patients

Question 10

Why might repeated examination be worthwhile when trying to work out the cause of a fever?

Answer 10

Symptoms of the fever are often fleeting - go away and come back

You might miss things if you only do one examination. Perhaps the patient has developed a new murmur or a rash?

Question 11

Initial investigations for a fever of unknown origin?

Answer 11

Chest X-Ray

Urinalysis and urine microscopy

Full blood count and differential white cell count

C-Reactive Protein and Erythrocyte Sedimentation Rate (acute phase reactants)

Blood cultures taken at times of fevers - at least 3 sets

Urea, creatinine, electrolytes, liver function tests

Question 12

A new murmur would lean towards which diagnosis?

Which further investigations would you do?

Answer 12

Endocarditis

Further investigations: echocardiography (trans-oesophageal echo)

Question 13

A patient presenting with headaches would lean towards which diagnosis?

Which further investigations would you do?

Answer 13

Temporal arteritis/giant cell arteritis

Temporal artery biopsy

Question 14

If you pick up on tropical travel in the history which further investigations should you carry out?

Answer 14

Blood for malarial parasites, Dengue or HIV

And bone marrow for leishmaniasis - parasites spread by the bite of phlebotomine sand flies.

Question 15

Further investigations for suspected TB infection? (3)

Answer 15

Sputum smear
Bone marrow
Mantoux

Question 16

If you detect micro haematuria then which further investigations would you do?

Answer 16

Auto-antibodies +/- renal biopsy for polyarteritis

Ultrasound

Question 17

What do you have to be wary of in regards to immunocompromised patients presenting with an undiagnosed fever?

Answer 17

They may not develop the same anatomical changes from infection as ‘normal’ patients.

ie a neutropenic patient cannot produce abscesses because they don’t have the same white cell count as a ‘normal’ host

Question 18

Common imaging techniques (4)

Answer 18

CT PET
Ultrasound
CT
Trans-oesophageal echocardiogram

Question 19

You can’t always differentiate between infection and inflammation from imaging.

What might you do to differentiate between the 2?

Answer 19

Obtain tissue sample for culture and histology.

Bone marrow and liver are often examined as part of a blind investigation for things like Malignancy, TB, lymphoma.

Question 20

Why are patients with an unknown fever rarely given a random trial of drugs?

Answer 20

The treatment may mask new signs/symptoms have not yet developed, that might help to reach a diagnosis.

Also, toxicity

Question 21

Which disorders commonly respond well to steroid drugs?

Answer 21

Vasculitis - temporal arteritis usually responds within 48 hrs

Connective tissue disorder

So, steroids can sometimes be useful in diagnosis but you must be sure that using them won’t put the patient at risk

Question 22

What is fabricated fever?

Answer 22

When a patient has a real fever but it’s self-induced.

A rare form of child abuse where a parent or carer, exaggerates or deliberately causes symptoms of illness in the child.

In adults, a common cause = self-injection of things like soap, faecal material etc

Also known as Munchausen syndrome