Polycythemia vera and other polycythemia syndromes

Abstract

Polycythemia vera (PV) is an acquired clonal hematopoietic stem cell disorder characterized by the overproduction of red and white blood cells and platelets in the absence of any appropriate stimulus for these events. For this reason, it is considered one of the four myeloproliferative diseases, which include essential thrombocythemia, primary myelofibrosis (PM), and chronic myeloid leukemia, all diseases which reflect varying degrees of erythroid, myeloid, and megakaryocytic marrow hyperplasia. Polycythemia, in general, can be defined as an increase in the volume of circulating red cells per kilogram of body weight or, equivalently, an increase in the red blood cell mass. Clinically, this is expressed as an absolute increase in the number of red cells, usually but not always accompanied by corresponding increases in the hemoglobin and hematocrit. Polycythemia might occur as a result of a primary disease of unknown cause, PV, or as a secondary manifestation of other illnesses. In the past, the diagnosis of PV was often an exclusionary diagnosis; now it is made more easily because of the JAK2V617F molecular abnormality (vide infra) found in this disease. Untreated PV leads to thrombohemorrhagic complications and eventually to progressive myelofibrosis, anemia, and splenomegaly. © 2008 Springer Science+Business Media, LLC.