Should we consider polycythemia vera and essential thrombocythemia as one disease?
The similarities and the possible transitions between the two diseases have always been recognized.4,5 Over the last few years, the interest in clarifying to what extent they share common pathogenetic mechanisms and clinical manifestations has been increased by the demonstration that a single somatic mutation of the Janus kinase 2 (JAK2) gene can be found in the large majority of polycythemia vera patients while the same mutation is present in only about half of those with essential thrombocythemia.6,7 In particular, much effort has been devoted to investigating the possible role of JAK2 mutational status in the heterogeneity of essential thrombocythemia subjects. This heterogeneity includes clonality of proliferation and type of clinical manifestations.8,9 Recently, the results of a large prospective clinical study provided evidence that JAK2-positive essential thrombocythemia patients have a clinical phenotype similar to that of polycythemia vera subjects while being different from t
