On the molecular origins of the chronic myeloproliferative disorders: it all makes sense

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Abstract
The chronic myeloproliferative disorders share many features: the marrow is hypercellular and overproduces one or more of the formed elements of the blood in the absence of any apparent appropriate or pathologic stimulus; the exuberant hematopoiesis often also extends to one or more extramedullary sites. Based on studies using polymorphic genes, these disorders were shown to be clonal,7 thought to arise in a single, multipotent hematopoietic progenitor or stem cell, which comes to dominate the marrow and blood. Hematopoietic progenitor cells from the marrow or peripheral blood display altered growth properties, proliferating in serum containing cultures in the absence of exogenous hematopoietic growth factors.8 Marrow megakaryocytes are hyperplastic and variably dysplasia and are responsible for the myelofibrosis of these disorders, patients often display a tendency toward thrombotic and hemorrhagic complications in addition to their signs and symptoms related to expansion of each hematopoietic lineage. However, compared with patients with CML, transformation to acute leukemia is far less common, especially in the absence of therapy with known mutagenic agents. But despite these clinical and pathologic features, the diagnosis of an individual patient with isolated erythrocytosis or thrombocytosis is often difficult, and their treatment is usually a nonspecific suppression of hematopoiesis.