Do we know more about essential thrombocythemia because of JAK2V617F?

The discovery of the JAK2V617F mutation has triggered enormous interest and some progress in our understanding of the pathogenesis of myeloproliferative disorders. This article reviews its impact upon our knowledge regarding essential thrombocythemia. The discovery of JAK2V617F has led to the proposal that essential thrombocythemia, polycythemia vera, and primary myelofibrosis be discarded as separate diagnoses, and the rationale for this change is discussed. Simplified diagnostic criteria based upon testing for JAK2V617F are proposed. Interesting data are emerging regarding disease progression and risk of complications, specifically thrombosis, pregnancy loss, and perhaps progression to myelofibrosis. The JAK2V617F allele burden is emerging as a potentially important risk factor, although its measurement is not yet standardized. It also may serve as a tool for monitoring the effects of emerging novel therapies, which hold the potential to revolutionize treatment, ranging from reducing risk of complications to potential cure. As with many important scientific discoveries, however, although the discovery of the JAK2V617F mutation has helped us to move forward, there are many new questions and many old questions still unanswered.