Essential thrombocytosis

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  • Rare, chronic myeloproliferative neoplasm
  • Abnormal proliferation is seen in megakaryocytic line only
  • Typically in elderly
  • Generally asymptomatic

Clinical Features

Differential Diagnosis

Reactive thrombocytosis

Autonomous thrombocytosis

Spurious (false) thrombocytosis

  • Mixed cryoglobulinemia
  • Cytoplasmic fragments
  • Bacteremia



  • CBC
  • Chem 7
  • ESR
  • Bone marrow biopsy sometimes needed


Per the WHO guidelines, diagnosis of ET requires all of the following:

Major criteria
Thrombocytosis ≥ 450 x 109L
Megakaryocyte proliferation with little to no granulocyte or erythroid proliferation
Not meeting criteria for CML, PV, PMF, MDS or other myeloid neoplasm
No evidence of reactive thrombocytosis or presence of JAK2V617F or other clonal marker


  • ASA 81mg
  • Myelosuppressive agents (hydroxyurea, Interferon-α)
  • Anagrelide


Also See


  1. uptodate
  2. Tefferi, A, et al. The 2008 World Health Organization classification system for myeloproliferative neoplasms: order out of chaos. Cancer. 2009; 115(17):3842-7,