title: Polycythemia vera and essential thrombocythemia: 2012 update on diagnosis, risk stratification, and management.
abstract: BACKGROUND
  Polycythemia vera (PV) and essential thrombocythemia (ET) are myeloproliferative neoplasms primarily characterized by erythrocytosis and thrombocytosis, respectively. Other disease features include leukocytosis, splenomegaly, thrombohemorrhagic complications, vasomotor disturbances, pruritus, and a small risk of disease progression into acute myeloid leukemia or myelofibrosis.
  
  
  METHODS
  Almost all patients with PV harbor a JAK2 mutation. When PV is suspected, the presence of a JAK2 mutation confirms the diagnosis and its absence, combined with normal or increased serum erythropoietin level, excludes the diagnosis. Differential diagnosis of ET had to include chronic myelogenous leukemia and prefibrotic myelofibrosis. A JAK2 mutation is found in approximately 60% of patients with ET.
  
  
  METHODS
  Current risk stratification in PV and ET is designed to estimate the likelihood of thrombotic complications: high-risk is defined by the presence of age >60 years or presence of thrombosis history; low-risk is defined by the absence of both of these two risk factors. Presence of extreme thrombocytosis (platelet count >1,000 × 10(9)/L) might be associated with acquired von Willebrand syndrome (AvWS) and, therefore, risk of bleeding. Risk factors for shortened survival in both PV and ET include advanced age, leukocytosis, and history of thrombosis.
  
  
  METHODS
  Survival is near-normal in ET and reasonably long in PV. The 10-year risk of leukemic/fibrotic transformation is <1%/1% in ET and <3%/10% in PV. In contrast, the risk of thrombosis exceeds 20%. The main goal of therapy is therefore to prevent thrombohemorrhagic complications and this is effectively and safely accomplished by the use of low-dose aspirin (PV and ET), phlebotomy (PV) and hydroxyurea (high risk PV and ET). Treatment with busulfan or interferon-α is usually effective in hydroxyurea failures. Screening for clinically significant AvWS is recommended before administrating aspirin in the presence of extreme thrombocytosis.
authors.affiliation: Division of Hematology, Department of Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA. tefferi.ayalew@mayo.edu
authors.forename: Ayalew
authors.initials: A
authors.lastname: Tefferi
mesh_terms: D000208:Acute Disease; D000367:Age Factors; D000477:Alkylating Agents / Q000009:adverse effects / Q000627:therapeutic use; D000925:Anticoagulants / Q000627:therapeutic use; D001241:Aspirin / Q000627:therapeutic use; D002066:Busulfan / Q000009:adverse effects / Q000627:therapeutic use; D004252:DNA Mutational Analysis; D019468:Disease Management; D018450:Disease Progression; D006801:Humans; D006918:Hydroxyurea / Q000009:adverse effects / Q000627:therapeutic use; D016898:Interferon-alpha / Q000627:therapeutic use; D053614:Janus Kinase 2 / Q000235:genetics; D007951:Leukemia, Myeloid / Q000453:epidemiology / Q000209:etiology; D007958:Leukocyte Count; D018962:Phlebotomy; D011087:Polycythemia Vera / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics / Q000628:therapy; D016032:Randomized Controlled Trials as Topic / Q000706:statistics & numerical data; D018570:Risk Assessment; D016019:Survival Analysis; D013920:Thrombocythemia, Essential / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology / Q000628:therapy; D019851:Thrombophilia / Q000188:drug therapy / Q000453:epidemiology / Q000209:etiology; D013927:Thrombosis / Q000453:epidemiology / Q000517:prevention & control
chemical_list: D000477:Alkylating Agents; D000925:Anticoagulants; D016898:Interferon-alpha; C507924:JAK2 protein, human; D053614:Janus Kinase 2; D002066:Busulfan; D001241:Aspirin; D006918:Hydroxyurea