Essential thrombocythemia (ET) is a myeloproliferative neoplasm characterized by an expansion of the megakaryocytic lineage, leading to an isolated elevation of platelets. It increases the risk of both thrombosis and hemorrhage.
The disease has traditionally been a diagnosis of exclusion, requiring the absence of reactive conditions and other clonal disorders that may present with thrombocytosis. The discovery of mutations in JAK2 and MPL now allows for the positive identification of essential thrombocythemia in more than one-half of all cases.
Diagnosis of essential thrombocythemia is often when there is an "unexplained and persistent thrombocytosis" (platelet count >450 × 109/L). Several diagnostic criteria have been put forward, e.g. WHO 2008 and BCSH 2010 2.
The imaging features of essential thrombocythemia can be variable depending on the organ involved and the diagnosis is usually suspected when there are thromboses of various vessels or ischemic events such as recurrent strokes.
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