Hématologie
MENUEssential thrombocytemia: new advances in diagnosis and therapeutic management Volume 12, issue 5, Septembre-Octobre 2006
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- Key words: thrombocytosis, diagnosis
- DOI : 10.1684/hma.2006.0056
- Page(s) : 315-29
- Published in: 2006
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.