Essential thrombocythaemia

Keywords: Thrombocythaemia

Key Information

Appropriate Tests


Essential thrombocythaemia (ET) is a myeloproliferative neoplasm in which the haemopoietic stem cell proliferation leads to a predominant increase in platelet count.

Full blood count, Blood film; Bone marrow biopsy, aspiration and trephine.

JAK-2 mutation may be positive in 50% of patients with ET. Calreticulin (CALR) mutations have been reported in up to 67% of patients with non-mutated JAK-2. 

Other tests may be useful to exclude non-ET myeloproliferative neoplasms.

See also Myeloproliferative neoplasms







Splenic infarction


Thrombosis (arterial and venous)



May be from a local lesion. 

  • Platelet dysfunction

Variable abnormalities of platelet function have been described. The skin bleeding time does not predict spontaneous or surgical bleeding and is not indicated.

  • Acquired von Willebrand disease

See von Willebrand disease

Cytotoxic therapy 


Disease progression/transformation


Anaemia, especially

  • Iron deficiency

Disease progression or transformation to:


  • Primary myelofibrosis


  • Acute leukaemia


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