While persistence of one mutation in CR was frequent (affecting DNMT3A, U2AF1, TET2 and SRSF2), associated with older age, and did not affect outcome, the presence of two or more mutations was associated with a 2-year leukaemia-free survival of 19.8% compared with 64.9% for those with one or no mutations detected. The gene discussed is TET2; the disease is leukemia.