Eight out of the nine patients with MR-mutations that were considered AML-NOS by WHO17 had at least one mutation in a chromatin modifier gene (ASXL1, n = 4; ASXL2, n = 2; BCOR, n = 3, EZH2, n = 1, CREBBP, n = 1, KDM6A, n = 1), frequently with other MR-mutations. The gene discussed is KDM6A; the disease is acute myeloid leukemia.