Quesmed (polycythaemia)

Question 1

What is polycythemia?

Answer 1

An increase in haematocrit, red cell count and haemoglobin concentration.

Question 2

What is haematocrit?

Answer 2

The ratio of the volume of red blood cells to the total volume of blood.

Question 3

What is the underlying gene mutation associated with polycythemia?

Answer 3

JAK 2 mutation

Question 4

What are the 2 main types of polycythemia?

Answer 4

Can be relative or absolute

Question 5

What is relative polycythemia?

Answer 5

AKA pseudopolycythemia

Occurs when haemoglobin is elevated secondary to low plasma volume rather than low red cell number.

Question 6

What can relative polycythemia be seen in?

Answer 6

Dehydration

Diarrhoea and vomiting

Excess diuretic use

Fever

Chronic alcohol intake

Question 7

What is absolute polycythemia?

Answer 7

If the plasma volume is normal, polcythemia is absolute (meaning red cell number would be raised).

Question 8

What are the 2 types of absolute polycythemia?

Answer 8

Primary and secondary

Question 9

What is primary absolute polycythemia?

Answer 9

Excess and uncontrolled erythocytosis (high RBC count) that is independent of erythropoietin (EPO) levels

Question 10

How does the JAK 2 gene mutation influence polycythemia?

Answer 10

Mutations of the JAK 2 gene leads to uncontrolled production of blood cells (especially RBC’s).

Question 11

What is secondary absolute polycythemia?

Answer 11

Excess RBC production which is driven by raised EPO levels.

Question 12

When is secondary absolute polycythemia typically seen?

Answer 12

• Situations causing an appropriate rise in EPO i.e. chronic hypoxia (e.g. COPD or long times spent at high altitudes)
• Anabolic steroid use

Question 13

What are the specific primary features of primary polycythemia (raised RBC count independent of EPO levels)?

Answer 13

Hyperviscosity syndrome: chest pain, myalgia, weakness, headache, blurred vision and loss of concentration.

“Ruddy” complexion: red complexion and reddening of palms and soles, ear lobes, mucous membranes and eyes.

Splenomegaly

Question 14

What investigations are done for polycythemia?

Answer 14

FBC (Hb raised, raised WCC and platelets)

JAK 2 mutation (>95% cases)

Possible raised urate and impaired renal function.

Question 15

How can CML be distinguished from polycythemia?

Answer 15

Can exclude CML by doing cytogenic testing to check for “philadelphia” chromosome which is the translocation of chromosomes 9 and 22.

Question 16

What is venesection?

Answer 16

Effective method of lowering erythrocyte count rapidly.

Question 17

Treatment options for polycythemia?

Answer 17

• Carry out regular venesection
• Aspirin 75mg daily
• Cytoreductive therapy - suppresses erythropoietin in those where venesection is not effective or those with thrombosis risk.

Question 18

What are the options for cytoreductive therapy in polycythemia?

Answer 18

1st line: hydroxycarbamide - suppresses erythropoietin and causes macrocytosis.

2nd line: interferon, JAK 2 inhibitors (ruxolitinib)

3rd line: busulfan can be used if leukaemia risk

Question 19

Hydroxycarbamide is first line for polycythemia in younger patients. True/false?

Answer 19

False

Interferon is usually first line younger patients and hydroxycarbamide is second line.