Most patients with essential thrombocythemia harbor a mutation in one of three genes: JAK2 V617F (60%), CALR (20%) or MPL (3%). The disease is associated with an increased risk of thrombosis. Risk of thrombosis is estimated based on the presence of a JAK2 mutation, history of thrombosis, age older than 60, and cardiovascular risk factors; risk can be stratified into very-low, low, intermediate, and high risk. Low dose aspirin therapy is the cornerstone of treatment, except for those with very-low risk disease, and cytoreductive therapy with hydroxyurea or interferon alfa-2a should be initatied in those with high-risk disease. When used, the dose of cytoreductive therapy should be adjusted to target a platelet count of 100,000 to 400,000. Acquired von Willebrand Syndrome may be seen in patients with platelets > 1 million and may predispose to bleeding – important to rule out prior to starting treatment in patients with platelets at these levels!
References: Essential Thrombocythemia