Pyrexia of Unknown Origin

Question 1

Define pyrexia of unknown origin (3 criteria)

Answer 1

Classical definition:

• fever of 38.3°C or greater
• for at least 3 weeks
• with no identified cause after 1 week of inpatient investigations

NOTE: some of these pts will have investigations as oupatients

Question 2

State some questions you must ask when taking a history for pyrexia of unkown origin

Answer 2

• Chronology of symptoms
• Other signs of infection
• Recent infection
• Pet/animal exposure
• Travel
• Occupation
• Medications
• Family history
• Vaccination history
• Sexual contacts
• Screen for autoimmune disease
• Screen for malignancy

Question 3

State some common causes of pyrexia of unknown origin (think about categorising the causes to help you remember them)

Answer 3

• Infective
  
  • TB
  • Abscesses
  • Infective endocarditis
  • Brucellosis
  • HIV
• Autoimmune/connective tissue
  
  • Temporal arteritis
  • Rheumatoid
  • Wegner’s granulomatosis
• Neoplastic
  
  • Leukaemia
  • Lyphoma
  • Renal cell carcinoma
• Others
  
  • Drugs
  • Thromboembolism
  • Hyperthyroidism
  • Adrenal insufficiency

Question 4

Discuss what investigations you may do if a pt has pyrexia of unknown origin. NOTE: list is lenghty as exlcuding lots of things

Answer 4

​Bloods

• FBC
• U&Es
• LFTs
• Bone profile
• CRP
• Clotting
• TFTs
• Multiple blood cultures
• LDH
• Ferritin
• B12
• Folate
• Autoimmune screen

Micro/virology

• HIV
• Hep B &C
• Syphilis
• MSU
• Sputum cultures
• CMV & EBV serology

Imaging

• CXR
• CT thorax/abdo/pelvis
• ECHO

… and many more!

Question 5

Discuss some general points of mangement of pyrexia of unknown origin

Answer 5

• Aim to establish diagnosis
• Don’t start empirical treatment without speaking to senior first
• Often ask rheumatology & haematology to see PUO depending on presentation
• Stable pts can be managed as outpatients following a period of observation in hospital
• Patients with no diagnosis despire prolonged investigation have good prognosis