Epidemiology
Etiology
- The JAK2 (Janus kinase 2) oncogene codes for a non-receptor tyrosine kinase in hematopoietic progenitor cells. JAK2 is essential for the regulation of erythropoiesis, thrombopoiesis (megakaryopoiesis), and granulopoiesis.
- 98% of patients with polcythemia vera have a mutation in the JAK2 gene (gain of function) → ↑ tyrosine kinase activity → erythropoietin-independent proliferation of the myeloid cell lines → ↑ blood cell mass (erythrocytosis, thrombocytosis, and granulocytosis) → hyperviscosity and slow blood flow → ↑ risk of thrombosis and poor oxygenation.
Pathophysiology
Clinical features
- Pruritus: Itching typically worsens when the skin comes into contact with warm water (aquagenic pruritus).
- Complications
- Venous thrombosis
- Arterial thrombosis
- Hemorrhagic complications
Diagnostics
Tip
Erythrocytosis associated with normal oxygen saturation and decreased serum EPO levels is strongly suggestive of polycythemia vera.