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essential thrombocytosis


  • a myeloproliferative disorder characterised by a high platelet count of > 600 × 10^3/µL for at least 2 months
  • incidence ~ 20 new cases per 1 million population per year
  • mainly effects middle aged and elderly
  • similar to primary myelofibrosis, this condition is due to mutually exclusive acquired gene mutations:
    • 40-50% of cases are associated with a mutation in the JAK2 kinase (V617F) gene
    • 25% of cases are associated with calreticulin gene CALR exon 10 mutation
    • 5-10% of cases are associated with MPL gene mutations
  • prognosis is much better than for myelofibrosis with 10 yr survival rates > 90%, and 20 yr survival rates around 75% for JAK-2 or MPL mutations, and ~85% for CALR mutations
  • patients are at risk of:
    • thrombosis (risk is ~ double for JAK-2 patients compared with MPL or CALR, being ~20% over 10yrs and 30% over ~20yrs)1)
    • haemorrhage
    • throbbing and burning of the hands and feet due to the occlusion of small arterioles by platelets (erythromelalgia)
    • 3-4% evolve into AML
    • some develop myelofibrosis


  • low dose aspirin is often advised to prevent thrombosis but there may be an increased risk of bleeding if aspirin is initiated while the platelet count is very high
  • those at risk of complications or with very high platelet count, if not pregnant or lactating, consider either:
    • hydroxyurea
    • interferon-α
    • anagrelide - lower risk of DVT than with hydroxyurea but higher risk of arterial thrombus, severe bleeding and transformation to myelofibrosis
  • in paients who have life-threatening complications, the platelet count can be reduced rapidly using platelet apheresis
NEJM Dec 2013
essential_thrombocytosis.txt · Last modified: 2023/01/09 04:44 by wh

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