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अमूर्त

Bone Marrow Features and Natural History of BCR/ABL-Positive Thrombocythemia and Chronic Myeloid Leukemia Compared to BCR/ABLNegative Thrombocythemia in Essential Thrombocythemia and Polycythemia Vera

Jan Jacques Michiels, Fibo W.J. Ten Kate, Hendrik De Raeve, Alain Gadisseur4

The Hannover bone marrow (BM) classification distinguished three phenotypes of BCR/ABL-positive CML: CML of common type (CML.CT), CML with megakaryocyte increase (CML.MI) and CML with megakaryocyte predominance (CML.MP). BCR/ABL-positive essential thrombocythemia (Ph-positive ET) is featured by CML.MP bone marrow picture of small monolobulated megakaryocytes and is part of the CML spectrum as a malignant disease (neoplasia) with an obligate transition into acute leukemia of near to 100% after 10 years follow-up. The Hannover BM classification distinguished three primary prefibrotic BCR/ABL-negative (Ph-negative) myeloproiferative disorders (MPD)s: essential thrombocythemia (ET), polycythemia vera (PV) and chronic or primary megakaryocytic granulocytic myeloproliferation (CMGM/PMGM). The incidence of blasts crisis is low in the Phnegative MPDs ET, PV and CMGM. The risk of myelofibrosis is high in CMGM/PMGM, moderate in PV but low in Ph-negative ET. In BCR/ABL-positive thrombocythemia the platelets are small and indolent (non-reactive) and megakaryocytes are smaller than normal with hypolobulated nuclei caused by BCR/ABL induced maturation defect. BCR/ABL-positive thrombocythemia does not present erythromelalgic thrombotic or bleedings manifestations at increased platelet count in excess of 400 to 1500 × 109/L. The platelets and megakaryocytes in BCR/ABL-negative ET and PV are large due to growth advantage caused by constitutively activated by the JAK2V617F or MPL515 mutation. JAK2 and MPL mutated thrombocythemias are associated with a high risk on aspirin responsive plateletmediated inflammation and thrombosis in the end-arterial circulation (platelet thrombophilia).