Approach to Polycytaemia

Question 1

What is polycytaemia?

Answer 1

Raise in any blood cell

Question 2

What is the difference between a relative and absolute raise in RBC?

Answer 2

• Relative: proportional changes of RBC numbers in relation to plasma water)
  –Decreased plasma volume due to fluid shift or dehydration
• Absolute: true increase in RBC numbers due to erythropoiesis i.e. erythrocytosis

Question 3

Causes of relative polycytaemia?

Answer 3

*Decreased plasma volume due to fluid shift
*Dehydration
*Acute GI disease
*Severe hyperthermia
*RBC redistribution
*Splenic contraction
‑ Exercise
‑ Adrenalin release

Question 4

What is the difference between primary and secondary polycytaemia?

Answer 4

Primary = not due to increased erythropoietin
=chronic red blood cell leukaemia
Secondary = due to erythropoietin

Question 5

What is the difference between appropriate + inappropriate response?

Answer 5

appropriate = due to generalised hypoxia
inappropriate = not due to generalised hypoxia

Question 6

What causes appropriate secondary absolute polycytaemia?

Answer 6

*Severe heart disease
‑ Congenital right-left shunts (reverse PDA)
‑ Severe (chronic) lung disease
‑ Clinical signs due to underlying disease
*Other causes
‑ High altitude
‑ Alveolar hypoventilation
‑ (Rare haemoglobinopathies)

Question 7

What are the causes of inappropriate secondary absolute polycytaemia?

Answer 7

Caused by inappropriately increased EPO
* Renal tumours or other lesions causing localised
renal hypoxia

Question 8

What causes primary absolute polycytaemia?

Answer 8

*Well-differentiated myeloproliferative disorder
‑ Polycytaemia rubra vera/ chronic erythroid
leukaemia/primary erythrocytosis

Question 9

How would you treat absolute polycytaemia?

Answer 9

*Absolute: remove the underlying cause if possible
*Stabilise with phlebotomy
‑ Care maintaining normovolaemia
‑ Can be repeated every 4-8 weeks
‑ Chemotherapy (hydroxyurea) in case phlebotomy
not effective