Essential thrombocytemia: new advances in diagnosis and therapeutic management Volume 12, issue 5, Septembre-Octobre 2006


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AP-HP, hôpital Avicenne, Université Paris XIII, 125, rue de Stalingrad, 93009 Bobigny Cedex Service d’Hématologie Clinique, AP-HP, hôpital Lariboisière, 2 rue A. Paré, 75010 Paris, Service d’Hématologie biologique, Laboratoire Hématologie, Hôpital Morvan, 5, avenue Foch 29200 Brest, CHRU de Lille, 2, avenue Oscar Lambret 59037 Lille, Laboratoire d’Anatomie Pathologique, Hôpital St Louis, 2, rue de la Grange aux belles, 75010 Paris, <Paul-Andre.Bryon@Rockfeller.univ-lyon1.fr>, Médecine du sang, Hôpital Hurriez, Rue Michel Polonovski, 59037 Lille, Laboratoire d’Anatomie Pathologique, Hôpital Beaujon, 100 Bd Général Leclerc, 92118 Clichy, Laboratoire d’Hématologie, CHU Nord, Chemin de Bourrelys, 13015 Marseille, Service Hématologie, Clinique du Parc, Rue Emile Combes, BP 20, 34171 Castelnau le Lez, Service Hématologie, Clinique du Parc, Rue Emile Combes, BP 20, 34171 Castelnau le Lez, Service maladies du sang, CHU d’Angers, 4 rue Larrey, 49933 Angers, Unité de Biostatistiques Santé Publique, Hôpital Avicenne, 125, Av Stalingrad, 93000 Bobigny, Laboratoire d’Hématologie, Hôpital Cardiologique, Av Magellan, 33604 Pessac, Laboratoire d’Hématologie, CHU Nord, Chemin de Bourrelys, 13015 Marseille cedex 20, Service de Médecine Interne, Hôpital du Haut Lévêque, Av Magellan, 33600 Pessac

The diagnosis of patients with an increased platelet number follows traditionally a two steps model. The first one includes a distinction between thrombocytosis associated with Ph negative myeloproliferatives disorders and secondary thrombocytosis or primary thrombocytosis associated with inherited familial disorders, myelodyplasias or BCR/ABL positive chronic myelocytic leukemias. The second step still relies mainly upon a phenotypic distinction between polycythemia vera (PV), idiopathic myelofibrosis (IMF) and essential thrombocythemia (ET). The recent description of the V617F mutation of JAK2 together with the now well accepted statement that an increased number of giant megacaryocytes with cluster formation is the hall-mark of Ph negative MPDs have clearly improved the efficiency of the first step. However as the distribution of the JAK2 mutation among Ph negative MPDs does not segregate PV ET and IMF according to our present phenotypic classification, the diagnosis of ET still requires a total red cell volume determination and a precise evaluation of megacaryocytic dysplasia and of the reticulin network densification to separate this ET, PV and the patients with a prefibrotic, early fibrotic or fibrotic form of MPD. However the new distinction between V617F JAK2 mutated and non mutated ET confirms previous evidences in favor of the heterogenicity of the patients previously diagnosed according to the PVSG criteria. The role of the classification of a patient as a prefibrotic or early fibrotic MPD according to BM findings on the risks of progression toward myelofibrosis has already been suggested. The presence of the V617F JAK2 mutation has been associated at presentation with features ressembling PV and may predict a higher rate of polycythemic progression, but it is not related to the presence of early fibrotic or prefibrotic bone marrow findings. The incidence of these new subclassifications of ET patients on life expectancy, vascular complications, risk of clonal progression and treatment options has now to be evaluated extensively. Recently a large prospective randomised study comparing hydroxyurea plus aspirin to anagrelide plus aspirin at low dosage has suggested, in ET diagnosed according to the PVSG criteria, a difference in sensitivity to the treatment arm according to the JAK2 mutation status of the patients.