Essential thrombocythemia (ET) is a myeloproliferative neoplasm characterized by clonal overproduction of platelets and an increased risk of thrombohemorrhagic complications. Patients are risk stratified by driver mutation, age, and thrombotic history and treated to reduce the risk of thrombotic and hemorrhagic events. The significance of platelet number as a risk factor or treatment goal is unclear. Despite the preponderance of data failing to demonstrate an association, there exists a pervasive belief that higher platelet counts correlate with an increased thrombotic risk. In fact, the association between thrombocytosis and bleeding is more clearly supported. Variability in regional consensus guidelines contributes to the uncertainty. This article reviews the data that shed light on the importance of platelet count in patients with ET.
Andrew T. Kuykendall and Rami Komrokji
Aaron T. Gerds, Jason Gotlib, Prithviraj Bose, Michael W. Deininger, Andrew Dunbar, Amro Elshoury, Tracy I. George, Ivana Gojo, Krishna Gundabolu, Elizabeth Hexner, Gabriela Hobbs, Tania Jain, Catriona Jamieson, Andrew T. Kuykendall, Brandon McMahon, Sanjay R. Mohan, Vivian Oehler, Stephen Oh, Animesh Pardanani, Nikolai Podoltsev, Erik Ranheim, Lindsay Rein, Rachel Salit, David S. Snyder, Brady L. Stein, Moshe Talpaz, Swapna Thota, Pankit Vachhani, Martha Wadleigh, Katherine Walsh, Dawn C. Ward, Mary Anne Bergman and Hema Sundar
Eosinophilic disorders and related syndromes represent a heterogeneous group of neoplastic and nonneoplastic conditions, characterized by more eosinophils in the peripheral blood, and may involve eosinophil-induced organ damage. In the WHO classification of myeloid and lymphoid neoplasms, eosinophilic disorders characterized by dysregulated tyrosine kinase (TK) fusion genes are recognized as a new category termed, myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA, PDGFRB or FGFR1 or with PCM1-JAK2. In addition to these aforementioned TK fusion genes, rearrangements involving FLT3 and ABL1 genes have also been described. These new NCCN Guidelines include recommendations for the diagnosis, staging, and treatment of any one of the myeloid/lymphoid neoplasms with eosinophilia (MLN-Eo) and a TK fusion gene included in the 2017 WHO Classification, as well as MLN-Eo and a FLT3 or ABL1 rearrangement.