Myeloproliferative Disorders

Abstract

“Myeloproliferative syndrome” was a term coined by Dameshek (1960). Most hematologists today regard the myeloproliferative disorders (MPDs) as pathological entities that include polycythemia vera, essential thrombocythemia, agnogenic (primary) myeloid metaplasia and chronic myeloid leukemia. With the possible exception of essential thrombocythemia, they are considered to be panmyeloses, and are clonal hemopathies arising from the pluripotent stem cell (Adamson and Fialkow,1978). In each disease, there is an emphasis on the proliferation of one cell line. Thus, in polycythemia vera, erythropoiesis predominates; in essential thrombocythemia and chronic myeloid leukemia, thrombopoiesis and granulopoiesis are the predominant events, respectively. In agnogenic myeloid metaplasia fibrosis, which is found in the bone marrow, does not seem to be part of the myeloproliferation, and is probably a reactive process produced as a result of abnormal myeloid cell development. The most consistent abnormality in this group of diseases is the Philadelphia chromosome (Ph1) found in all the hematopoietic cell precursors of patients with chronic myeloid leukemia. The Ph1 represents reciprocal translation of sections of the long arms of chromosomes 9 and 22. The principal molecular event involves translocation of the Abelson proto-oncogene (c-abl) from chromosome 9 to the breakpoint cluster region (bcr) of chromosome 22, resulting in the formation of a chimeric bcr/c-abl gene (Champlin et al., 1986).KeywordsPolycythemia VeraEssential ThrombocythemiaMyeloproliferative DisorderExtramedullary HematopoiesisEssential ThrombocythaemiaThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.