Blood cell activation in myeloproliferative neoplasms

T he term classic BCR/ABL-negative myeloproliferative neoplasms encompasses three disorders, polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF), which originate in a single pluripotent hematopoietic stem cell and share several clinical, hematologic and histological features. These include bone marrow hypercellularity with variable degrees of fibrosis, overproduction of one or more of the blood cell lines, frequent splenomegaly, increased risk of thrombosis and bleeding, and the tendency to evolve into acute leukemia. Transition from one disorder to another is also occasionally observed. Recently, the discovery of the V617F mutation in the JAK2 gene in the majority of patients with a myeloproliferative neoplasm has provided biological support to the inclusion of the three diseases within the same