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POLYCYTHEMIA VERA (PV)

Epidemiology

  • MC in older people
  • Exposure to ionizing radiation is predisposing factor

Pathogenesis

  • Characterised by increase in RBC mass – ↑Hb + ↑Hct
  • Clonal disorder of hematopoietic stem cells
    • Erythroid precursors are able to grow independent of erythropoietin
  • Main complications of PV – thrombosis and haemorrhage
  • Patients may develop a ‘burnt out’ stage – characterised by BM fibrosis (30% patients)
  • Occasionally patients can transform to AML

Clinical features

  • Symptoms are usually due to high blood viscosity, splenomegaly, bleeding and hypermetabolism
  • ↑blood viscosity
    • Headache, dizziness, tinnitus, numbness in fingers, dyspnoea on exertion, strokes, cardiac cyanosis
  • Splenomegaly – LUQ discomfort, early satiety
  • Bleeding – from mucous membranes, skin, GIT
  • Hypermetabolism – gout, renal stones
  • Prutitis after taking a hot shower
  • Physical exam – ruddy complexion, blotchy skin

Diagnosis

  • ↑Hb, Hct, RCC
  • ↑WCC – due to granulocytosis
  • ↑platelets
  • Blood smear is unremarkable
  • ↑LDH, UA
  • ↓ EPO
  • WHO diagnosis
  • Bone marrow
    • Hypercellular – increase in all cell lines
    • Mild fibrosis (30% patients progress from PV >MF)
    • Absence of stainable iron – characteristic feature
  • Cytogenetics – JAK-2 mutation is strong indicator of PV (on chromosome 9)

Disease course

  • Median survival – >10 years
  • Thrombosis – MCC of death in pts with PV
    • DVT, PE, strokes
  • Progressive MF
    • Patients can progress to a ‘burnt out’ stage with MF – can resemble idiopathic MF
  • Transformation to AML
    • Increased risk of transformation in patients receiving chemo with chlorambucil or radioactive phosphorus

Treatment

  • Phlebotomy – main treatment
    • Controls the Hct level by inducing a state of Fe deficiency
    • 500ml of blood removed every 2-3 days until Hct is between 42-45%
  • Hydroxyurea – Controls Hct, WCC and platelet count
  • Interferon-a – Same effect as hydroxyurea
  • Low dose aspirin – to prevent thromboses
  • Radioactive phosphorus – in older patients
    • Increases risk of transformation to AML
  • Anagrelide – selectively decreases platelet count
  • Allopurinol [300mg]
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