Polycythemia Vera

BASICS

DESCRIPTION

  • Polycythemia vera (PV) is a chronic myeloproliferative neoplastic disorder marked by overproduction of red blood cells (erythrocytosis) which most often is diagnosed after 60 years of age. It is caused by a JAK2 mutation and is typically discovered incidentally on CBC (increased H/H; often increased WBC and platelets too). The most frequent initial symptoms are pruritus, splenomegaly, or vasomotor abnormalities.
  • Morbidity and mortality are primarily related to complications from blood hyperviscosity leading to venous or arterial thrombosis and/or from leukemic transformation or myelofibrosis (MF).
  • The average survival after diagnosis of untreated PV is 6 to 18 months, but with adequate treatment, median survival is 13 years.
  • Synonyms: primary polycythemia; PV rubra; Osler-Vaquez disease

EPIDEMIOLOGY

Incidence

  • Median age at diagnosis: 61 years, one-quarter of cases present prior to age 50, and 10% prior to age 40
  • Incidence in the United States in 2012: 2.8/100,000 population of men and 1.3/100,000 population of women; highest for men aged 70 to 79 years at 23.5/100,000 persons per year

Prevalence

In the United States in 2010, estimates ranged from 45 to 57 cases per 100,000 patient.

ETIOLOGY AND PATHOPHYSIOLOGY

Caused by a JAK2 (tyrosine kinase) mutation which causes abnormal stem cells to suppress normal stem cells and turns on uncontrolled activation of hematopoietic signaling, particularly of the erythroid line and, to a lesser extent, the myeloid and megakaryocytic lines

Genetics

Most cases are not inherited. They are caused by either a JAK2 V617F mutation (95%) or a JAK2 exon 12 mutation (4%). Compared with heterozygous mutations, homozygous mutations are associated with worse disease outcomes, including more severe symptoms and higher likelihood of disease progression (1).

RISK FACTORS

  • Almost none
  • Rare familial disposition but most cases are not inherited.
  • Possible association with exposure to ionizing radiation or other toxins but most cases have no exposure risk.

GENERAL PREVENTION

None

COMMONLY ASSOCIATED CONDITIONS

  • Arterial emboli (including ischemic digits, myocardial infarction, transient ischemic attack [TIA], stroke)
  • Venous emboli (including DVT, pulmonary embolism, splanchnic thrombosis leading to complications like Budd-Chiari and splenomegaly)
  • Major or microhemorrhage (including acquired von Willebrand disease)
  • Gout
  • Acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS)
  • Secondary MF

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