Polycythaemia

Question 1

Define polycythaemia

Answer 1

INCREASE in haemoglobin, packed cell volume (PCV) known as HAEMATOCRIT and red cell count

(note these measurements are concentrations, thus dependent on plasma volume and RBC mass)

Question 2

What is a better indicator of polycythaemia of PCV or Hb?

Answer 2

PCV

Question 3

What two groups can polycythaemia be divided into?

Answer 3

Absolute i.e. due to increase in RBC mass

Relative i.e. decreased plasma volume and RBC mass

Question 4

What 2 subgroups can absolute polycythaemia be divided into?

Answer 4

Primary and Secondary

Question 5

Give examples of Primary Absolute polycythaemia or what it is

Answer 5

Polcythaemia Vera (PV)
Mutations in erythropoitin receptor
High oxygen affinity Hbs

Question 6

Give examples of Secondary Absolute polycythaemia or what it is

Answer 6

Hypoxia due to:
High altitude, Chronic lung disease, cyanotic congenital heart disease or heavy smoking
Inappropriately high erythropoietin secretion e.g. in renal carcinoma and hepatocellular carcinoma

Question 7

Subgroups of Relative polycythaemia (decreased plasma volume and normal RBC mass)

Answer 7

Apparent polycythaemia

Dehyrdration

Question 8

Is apparent polycythaemia an acute or chronic form and what is it associated with?

Answer 8

Chronic
Associates with:
Obesity, Hypertension, High alcohol and Tobacco intake

Question 9

Is Relative polycythaemia as a result of dehydration an acute or chronic condition and give example what what can cause this

Answer 9

Acute

Dehydration causes by alcohol or diuretics

Question 10

Pathophysiology of Polycythaemia Vera

Answer 10

Neoplastic proliferation and maturation of erythroid, megakaryocytic and granulocytic elements.

A clonal stem cell disorder resulting in a malignant proliferation of a clone derived from one pluripotent marrow stem cell.
Erythroid progenitor offspring do not need ERYTHROPOIETIN to avoid apoptosis. This results in excess proliferation of RBCs, WBCs and platelets which causes increased haematocrit (packed cell volume) resulting in hyperviscosity and thrombosis.
Major complications are thrombosis and haemorrhage.

Question 11

Aetiology of polycythaemia vera

Answer 11

Somatic mutation in a single haematopoietic stem cell

Question 12

How many cases of polycythaemia vera are there per year?

Answer 12

2/100,000

Question 13

Diagnostic tests of Polycythaemia vera

Answer 13

Haematocrit is high and Hb

JAK2 testing can be negative, but presence of JAK2 mutation on genetic screen is a major criteria.

Question 14

What is JAK2

Answer 14

Janus Kinase 2
Cytoplasmic tyrosine kinase that transudces signals, especially those triggered by haemopoietic growth factors such as erythropoietin

Question 15

Clinical presentation of Polycythaemia vera

Answer 15

Can be asymptomatic
Pruritus, particularly after exposure to warm water.
Headaches, dizziness and sweating.
Thrombotic complications: MI, stroke, DVT
Rare but classic: Erythromelalgia (sudden severe burning pain in hands or feet, with red/blue coloration of the skin)

Question 16

Complications of untreated Polycythaemia vera

Answer 16

Can transform into acute myeloid leukemia.

Thrombotic events

Question 17

Treatment of Polycythaemia Vera

Answer 17

(treatment aims to maintain a normal blood count)
Venesection to low PCV and normal blood count.
Chemotherapy - Hydroxycarbamide and low-dose Bulsulfan for those who dont tolerate venesection
Seek to prevent thrombosis with low dose ASPIRIN
Intermittent long term phlebotomy
Possible myelosuppression.

Question 18

What is given to those over 70 with polycythaemia vera due to increased acute leukemia

Answer 18

Radioactive phosphorus

Question 19

What can be given to block uric acid production and thereby reduce gout

Answer 19

Allopurinol