a myeloproliferative disorder caused by clonal proliferation of a marrow stem cell leading to an increase in red cell volume, often accompanied by overproduction of neutrophils and platelets.

Epidemiology: The incidence of polycythaemia vera peaks in the sixth decade.

Aetiology:

• It has recently been established that a mutation in JAK2 is present in approximately 95% of patients with polycythaemia vera and this has resulted in significant changes to the diagnostic criteria.
• The JAK2 mutation causes uncontrolled and excessive proliferation and maturation of:
  • haematopoeitic stem cells - myeloid stem cells - proerythroblasts - red blood cells

Risk factors:

• Advancing age - rarely diagnosed before 40
• Hx of Budd-chiari syndrome
• Family Hx

PC

• pruritus, typically after a hot bath
  • also have proliferation of mast cells, high temperature causes degranulation of these mast cells causing itching
• plethoric appearance - excess of blood causing a red complexion (congestion)
• Bruising
• Abdominal discomfort
• visual disturbance
• headache