Polycythemia Vera

Description

• Polycythemia vera (PV) is a myeloproliferative clonal stem cell disorder marked by increased production of red blood cells (erythrocytosis) with excessive erythroid, myeloid, and megakaryocytic elements in the bone marrow.
• Morbidity and mortality are primarily related to complications from blood hyperviscosity leading to thrombosis development as well as malignant transformation. Untreated patients may survive 6 to 18 months. Adequate treatment may extend life to >10 years.
• Myelofibrosis (MF) can develop in the bone marrow, leading to progressive hepatosplenomegaly.
• Synonyms: primary polycythemia; maladie de Vaquez disease; primary PV; PV rubra; polycythemia, splenomegalic; Vaquez-Osler disease

Epidemiology

Incidence

• Predominant age: 50 to 75 years; however, can occur in early adulthood and childhood
• Predominant sex: male > female (slightly)
• 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 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 patients.

Etiology and Pathophysiology

JAK2 V617F mutation associated with clonal proliferative disorder

Genetics
JAK2 V617F (tyrosine kinase) mutation: >97% of patients with PV have an activating mutation; this is helpful in differentiating from secondary erythrocytosis. Homozygote carriers will have higher incidence of symptoms such as pruritus but will not have higher incidence of disease than heterozygotes.

Risk Factors

• PV may be slightly more prevalent among Jews of Eastern European descent than other Europeans or Asians.
• Familial history is rare.

Commonly Associated Conditions

• Budd-Chiari syndrome
• Ischemic digits
• Mesenteric artery thrombosis
• Myocardial infarction
• Cerebrovascular accident or transient ischemic attack
• Venous thromboembolism and pulmonary embolism