Biology and Current Treatment of Myeloproliferative Neoplasms

The classical myeloproliferative neoplasms (MPN) are characterized by clonal expansion of one or more hematopoietic cell lineages and are driven by mutations that activate constitutive signaling via JAK2 pathway. The criteria for diagnosis have now been defined by the World Health Organization (WHO) and the term MPN as is currently used encompasses the entities of primary myelofibrosis, polycythemia vera, and essential thrombocytosis. There is imperfect correlation between the genotype and disease phenotype in MPN and the latter is determined by a variety of patient factors that are independent of the driver mutation. The disease course in MPN can span decades and accurate risk assessment is critical in the choice of therapy and treatment is largely geared toward prevention of complications and providing symptomatic relief. Although new agents have been approved in recent years, no therapy has been convincingly shown to alter disease progression and allogeneic hematopoietic stem cell transplantation (HCT) remains the only curative therapy known to date.