Janus kinase 2 gene(JAK2) mutation was the first driver mutation to be discovered in essential thrombocytosis and is present in roughly 50% of cases.
The presence of a JAK2 V617F mutation supports the diagnosis, it is not however specific to essential thrombocytosis and can be present in other myeloproliferative neoplasms.
JAK2 mutations has been linked to increased frequency of disease complications, especially thrombosis in essential thrombocytosis.
Jak2 V617F mutation present in >95% of patients with polycythemia vera, and in 50-60% of patients with essential thrombocytosis and primary myelofibrosis.