hematology and oncology
Overview of Myeloproliferative Neoplasms
Introduction
Myeloproliferative neoplasms are clonal proliferations of bone marrow hematopoietic stem cells, which can manifest as an increased number of functionally normal platelets, red blood cells (RBCs), or white blood cells (WBCs), alone or in combination, in the circulation and sometimes with fibrosis in the bone marrow and extramedullary hematopoiesis (cell production outside the marrow). Based on these abnormalities, they are classified as Essential Thrombocythemia (increased platelets) Primary Myelofibrosis (PMF) (marrow fibrosis or scarring) Polycythemia Vera (any combination of increased WBCs, RBCs, and platelets but rarely erythrocytosis alone) Chronic Myeloid Leukemia (CML) (associated with the Philadelphia chromosome and expression of Essential thrombocythemia, primary myelofibrosis, and polycythemia vera can spontaneously transform to Acute leukemias . Essential thrombocythemia and polycythemia vera transform to acute leukemia at very low rates in the absence of prolonged exposure to chemotherapeutic agents such as Less common myeloproliferative neoplasms include the Hypereosinophilic Syndrome and Each disorder is identified according to its predominant features (see table). Although proliferation of one or more hematopoietic cell types dominates the clinical picture in each of these disorders, all 3 are caused by clonal proliferation of a pluripotent hematopoietic stem cell, causing an increased proliferation of normal RBC, WBC, and platelet progenitors in the bone marrow. This abnormal clone does not, however, produce bone marrow fibroblasts, which can proliferate in a polyclonal, reactive, and reversible fashion in response to the abnormal stem cell. ) gene is also mutated in a significant proportion of essential thrombocythemia and primary myelofibrosis patients and rarely in Polycythemia Vera . Disorder Disorder Predominant Feature Predominant Feature Essential Thrombocythemia None Thrombocytosis Sometimes leading to bone marrow fibrosis, most often in males Primary Myelofibrosis (PMF) None Anemia, leukocytosis, thrombocytosis, and bone marrow fibrosis with extramedullary hematopoiesis Polycythemia Vera None Erythrocytosis usually with concurrent increased white blood cell and platelet counts and sometimes extramedullary hematopoiesis Chronic Myeloid Leukemia (CML) None Granulocytosis and/or thrombocytosis 