In a multicenter series of 32 consecutive cases, complete remission was achieved by 44% of patients and was more likely to occur in the absence of pre-leukemic PV/post-PV MF, complex karyotype, and NRAS/KRAS mutations, with no correlation with neither TP53 nor IDH1/IDH2 mutational studies. The gene discussed is IDH2; the disease is acquired polycythemia vera.