myeloproliferative disorder. neoplastic proliferation of erythroid cells in bone marrow

Definition: myeloproliferative disorder affecting red cells but may affect platelets additionally

Epi: older age (>60y)

Risk factors: nil

Pathophys: activation mutation in JAK2 gene → haematopoesis becomes EPO-independent → increase red cell mass production

• JAK2 V617F gain-of-function mutation. JAK2 is an oncogene that encodes a non-receptor tyrosine kinase in haematopoietic progenitor cells. This mutation causes increased tyrosine kinase activity → EPO-independent proliferation of the myeloid cell lines (RBCs, granulocytes Plts) in the marrow → Increased blood cell mass (RBCs, granulocytes, plts).

Clinical Features

• asymptomatic
• Facial plethora
• Hypertension, dizziness, headaches, visual disturbances due to blood hyper-viscosity.
• hepatosplenomegaly (from secondary erythropoiesis)
• Bleeding due to BV damage, plt abnormality.
• Pruritus (especially after having a warm shower) due to increased granulocytes (mast cells, basophils = histamine) → PATHOGNOMONIC!
• Erythromelalgia (red hands and feet).
• arterial/venous thrombosis (High viscosity → vascular stasis→ infarctions)

Investigations: