IFNα has become one of the major therapies in ET and PV for two reasons: (a) the toxicity of IFNα has been alleviated by using prolonged half-life type 1 IFN, and (b) it is the only available treatment that can act on the clonal disorder and may induce a deep molecular remission (in 25% of the cases)57. This evidence concerns the gene IFNA1 and essential thrombocythemia.