Myeloproliferative Neoplasms: An Overview

INTRODUCTION The myleproliferative neoplasms (MPNs) are a closely related group of clonal stem cell hematologic blood disorders characterized by an increase in one or more cell lines of the bone marrow. The proliferation of red blood cells (RBCs), white blood cells (WBCs) or platelets is usually mature in morphology. The MPNs have overlapping clinical features but different etiologies. The original name of these disorders was the myeloid proliferative disorders or MPDs proposed by William Damashek in 1951;¹ they were renamed by the World Health Organization (WHO) in 2008 to “myeloproliferative neoplasms”² due to new findings. The 2008 WHO classification of MPNs has added new entities, including chronic myelogenous leukemia, Philadelphia chromosome-positive (CML); chronic neutrophilic leukemia (CNL); polycythemia vera (PV); primary myelofibrosis (PMF); essential thrombocythemia (ET); chronic eosinophilic leukemia, not otherwise specified (CEL/NOS); mastocytosis; and myeloproliferative neoplasm, unclassifiable (MPN-U). The identification of numerous molecular mutations such as the “breakpoint cluster region/Abelson fusion 1 (BCR/ABL1) mutation, Janus kinase 2 (JAK2) mutation, (JAK2), myeloproliferative leukemia virus oncogene homolog (MPL) and others,, has contributed to the further understanding of the genetic complexity of the MPNs. The current classification of the MPNs is based on clinical presentation, pathologic descriptions, histological information, and genetic mutations. The genetic mutations or molecular markers have become essential for diagnosis, prognosis and treatment of these disorders.

The MPNs are characterized by a hypercellular bone marrow due to unregulated cell proliferation. Usually one cell line is increased, but all may be elevated. The classification is based on which cell line is…