Larger studies are needed to assess whether mutations in TET2 and/or other genes that regulate the HSC compartment (such as DNMT3a and IDH1/2) result in persistence of malignant clones during IFN-alpha2 therapy and if their persistence indeed impact upon the prognosis of ET and PV patients being treated long-term with IFN-alpha2. Here, IDH1 is linked to acquired polycythemia vera.