Essential thrombocythaemia (ET)

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 (1).

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 (2):

Life expectancy of patients with essential thrombocythaemia (ET) is reported to be modestly reduced compared with that of the general population. Median overall survival (stratified by age) has been estimated to be:

• 35 years (age ≤40 years)
• 22 years (age 41 to 60 years)
• 11 years (age >60 years)

Development of either AML or myelofibrosis is uncommon (3).

References:

1. Ashorobi D, Gohari P. Essential Thrombocytosis (Essential Thrombocythemia, ET). StatPearls 2020.
2. Szuber N, Vallapureddy RR, Penna D, et al. Myeloproliferative neoplasms in the young: Mayo Clinic experience with 361 patients age 40 years or younger. Am J Hematol. 2018 Dec;93(12):1474-84.
3. Cerquozzi S, Tefferi A. Blast transformation and fibrotic progression in polycythemia vera and essential thrombocythemia: a literature review of incidence and risk factors. Blood Cancer J. 2015 Nov 13;5:e366.