Polycythaemia (Primary And Secondary)

Question 1

Definition

Answer 1

Erythrocytosis of any cause

Question 2

Aetiology Primary

Answer 2

Polycythaemia Vera - JAK2V617 mutation
Congenital or acquired

Question 3

Aetiology secondary

Answer 3

Hypoxia
Increase in EPO (e.g. RCC, renal cysts)
Dehydration
Alcohol
On testosterone

Question 4

Epidemiology + Risk factors

Answer 4

Common in over 60’s
Budd chiari syndrome

Question 5

Pathophysiology

Answer 5

• relative polycythaemia = decrease in total plasma
• absolute polycythaemia = increase in total volume of RBCs
  Polycythaemia Vera: Mutation of Janus Kinase 2 (JAK2) gene
  Normally kidney produces erythropoietin = binds to receptors on the haematopoietic stem cells = activates JAK2 gene = cell divides + produces more RBCs
  With mutation JAK2 always active
  Over time the bone marrow is replaced by scar tissue = myelofibrosis = response to cytokine release from the proliferating cells = SPENT PHASE
  This effects production of other blood cells = can lead to anaemia, low WBCs etc
  The production can happen in other areas such as the spleen or liver (extra-medullary haematopoeisis) = hepatosplenomegaly
  Due to the high PCV, there is hyper-viscosity = increase risk of thrombosis.

Question 6

Symptoms

Answer 6

May be asymptomatic + only detected on FBC
Headaches
Dizziness
Tinnitus
Visual disturbances
Itching after a hot bath = due to lots of basophils and mast cells releasing histamine
Erythromelalgia = burning sensation in fingers and feet

Question 7

Signs

Answer 7

Facial plethora = swollen blood vessels in facial skin causing redness + red conjunctiva
Splenomegaly
Gout may occur due to increase in urate from RBC of turnover
Features of arterial (cardiac, cerebral, peripheral) or venous (DVT, cerebral, hepatic) thrombosis may be present.

Question 8

Diagnosis

Answer 8

FIRST LINE = Bloods
- Increase in: red cell count, Hb, haematocrit, pcv, wbc, platelets, B12
GOLD STANDARD = CYTOGENIC - positive for JAK2 gene mutation
USS = Splenomegaly
Bone marrow biopsy =
- hypercellularity with erythroid hyperplasia
- maybe presence of fibrous tissue

Question 9

Treatment

Answer 9

FIRST LINE = Venesection (if low risk of thrombosis = younger patients) to haematocrit >45% in both males and females
- removal of blood from vein regularly
LOW RISK (no Hx of thrombosis, age <60) = Aspirin twice daily prevent blood clots
HIGH RISK = Chemotherapy with hydroxycarbamide (AKA hydroxyuria) to reduce RBC numbers
- side effects = GI upset, pancytopenia is most serious SE
- a-interferon is preferred in women of child bearing age