Management of MPN beyond JAK2.

Thrombocytosis has a large number of potential underlying causes, but the dominant group of hematological conditions for consideration in this setting are the myeloproliferative neoplasms (MPNs). In this chapter, we consider several key linked questions relating to the management of thrombocytosis in MPNs and discuss several issues. First, we discuss the differential diagnosis of thrombocytosis, which myeloid disorders to consider, and practical approaches to the discrimination of each individual MPN from other causes. Second, there have been several major advances in our understanding of the molecular biology of these conditions and we discuss how these findings are likely to be practically applied in the future. Third, we consider whether there is evidence that thrombocytosis contributes to the complications known to be associated with MPN: thrombosis, hemorrhage and transformation to leukemia and myelofibrosis. Last, we review current ideas for risk stratification and management of essential thrombocythemia and polycythemia vera as the 2 entities within the MPN family that are most frequently associated with thrombocytosis.