From the 26 patients with at least one RUNX1 O/LO mutation, 16 were diagnosed with AML-RUNX1m and the other 10 with AML-MRC, because of the presence of MLD (n = 8), MDS history (n = 6, all with concurrent MLD) or MDS-defining cytogenetics (n = 2). The gene discussed is RUNX1; the disease is myelodysplastic syndrome.