essential thrombocythaemia (ET)

Last reviewed 01/2018

Essential thrombocytosis is primarily a diagnosis of exclusion. Other causes to be ruled out are a reactive thrombocytosis, and thrombocytosis seen in other myeloproliferative diseases.

The patient usually presents with bruising, bleeding and cerebrovascular symptoms. The spleen may be enlarged early in the disease but then is reduced, and may possibly atrophy, as a result of recurrent thromboses.

Very small or giant platelets are often present. The bone marrow is hypercellular with an increased number of megakaryocytes, many of which are often abnormally shaped and clustered. The white cell count may be normal or elevated.

Prognosis:

• in the first decade of the disease, median survival is close to that of an age-adjusted normal population and the greatest morbidity and mortality stems from thrombohaemorrhagic complications
• overall incidence of thrombosis (superficial or deep) reported to be 20–40%. However, the incidence of major thrombotic events such as stroke, myocardial infarction or deep venous thrombosis is only 10–20% at diagnosis or during follow-up

Reference:

1. Griesshammer M et al. Essential thrombocythaemia and pregnancy. Leukemia & Lymphoma 1996;22 (supp.1): 57–63.