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Diagnosis and clinical manifestations of essential thrombocythemia

Author
Ayalew Tefferi, MD
Section Editor
Stanley L Schrier, MD
Deputy Editor
Alan G Rosmarin, MD

INTRODUCTION

Essential thrombocythemia (ET) is one of the chronic myeloproliferative neoplasms (MPNs), which are collectively characterized by clonal proliferation of myeloid cells with variable morphologic maturity and hematopoietic efficiency. ET has also been called essential thrombocytosis and primary thrombocytosis. It is characterized by excessive, clonal platelet production with a tendency for thrombosis and hemorrhage. (See "Overview of the myeloproliferative neoplasms".)

The clinical manifestations and diagnosis of ET will be reviewed here. The prognosis and treatment of this disorder are presented separately as is the general approach to the patient with an elevated platelet count. (See "Approach to the patient with thrombocytosis" and "Prognosis and treatment of essential thrombocythemia" and "Overview of the myeloproliferative neoplasms".)

PATHOGENESIS

The pathogenesis of ET is not completely understood. ET is a clonal stem cell disorder and the increased platelet counts are a result of excessive platelet production and not prolonged platelet survival in the peripheral blood.  

Approximately 90 percent of cases have a somatically acquired driver mutation in JAK2, CALR, or MPL. These mutations result in the upregulation of JAK-STAT target genes, demonstrating the central importance of this pathway in the pathogenesis of ET. Ongoing investigations are aimed at determining the significance of these and other mutations in the genesis of ET and the other myeloproliferative neoplasms as well as their relative roles in determining disease phenotype, leukemic transformation, and the level of involvement of stem cells in these disorders. This is described in more detail separately. (See 'Genetic features' below and "Overview of the myeloproliferative neoplasms", section on 'Mutations in PV, ET, and PMF'.)

While most cases of ET appear to be sporadic, families with an increased incidence of ET have been described [1,2]. Familial cases are thought to be due to a genetic predisposition to acquire somatic mutations rather than to direct inheritance of germline mutations.  

                        

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Literature review current through: Nov 2016. | This topic last updated: Fri Nov 11 00:00:00 GMT 2016.
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