Polycythaemia vera

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Polycythaemia vera (PV) is an MPN characterised by trilinear proliferation, i.e. growth of erythroid, granulocytic, and megakaryocytic cell lines, causing elevation of all three types of blood cells in the blood. It’s caused by an acquired gain-of-function mutation in the JAK2 gene which makes myeloid cells proliferate independently of the hormone EPO.

Clinical features

Despite an increased blood cell mass, most people are asymptomatic. However, the increased viscosity can cause hyperviscosity syndrome, consisting of mucosal bleeding, neurological symptoms, and visual changes. It can also predispose to both thrombosis and haemorrhage. Thrombosis can be venous (renal vein, mesenteric vein, portal vein, etc.) or arterial (stroke, MI). Hepatosplenomegaly is typical.

Diagnosis and evaluation

Labs show:

  • Elevated Hct
  • Elevated RBC
  • Elevated WBC
  • Elevated thrombocytes
  • Decreased EPO

Blood smear shows normal cell morphology. Bone marrow biopsy shows a hypercellular bone marrow with trilinear proliferation. Genetic testing for JAK2 mutation confirms the diagnosis.

Treatment

The basic treatment is therapeutic phlebotomy to reach normal Hct levels and aspirin to prevent thrombosis. If there is a history of thrombosis or the patient is >60 years, cytoreductive therapy is also indicated. This involves cytoreductive drugs like hydroxyurea or pegylated interferon.