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Essential thrombocytemia : advances in risk stratification for thromboses and survival Volume 19, issue 6, Juin 2007

Author
AP-HP, Hôpital Lariboisière, Service d’Hématologie Biologique, 2 rue Ambroise Paré, 75010 Paris, Université Paris 7 Denis Diderot, Faculté de Médecine, Site Villemin, 10, avenue de Verdun 75010 Paris

Essential thrombocytemia (ET), a Philadelphia chromosome negative myeloproliferative syndrome, is a clonal disorder of the hemopoietic stem cell characterized by a thrombocytosis accompanied by moderate leukocytosis and even mild anemia. The V617F mutation on the JAK2 tyrosine kinase which was first reported in 95 % of Polycythemia Vera cases was also found in about 50 % of ET cases thus defining a special subgroup. Arterial or venous vascular manifestations and disturbances of the microcirculation are the main clinical complications ; their physiopathological mechanism involves platelets and leukocyte hyperactivation and even, although less marked, a vascular endothelial cell activation. The stratification of the vascular risk relies on data of a retrospective control/case study which showed that patients above 60 years and/or with previous thomboses presented a higher rate of thromboses, constituting the high vascular risk subgroup. A new retrospective study showed evidence that leukocytosis also constitutes an other risk factor for thrombosis. Finally, for the first time risk factors for survival and transformation to leukemia are proposed. The V617F JAK2 mutation does not seem to constitute a predictive factor for thrombosis or for survival. If data are confirmed, they will provide a new stratification of ET and will help therapeutic management.