Although mutations appear to be rare events, there is evidence which indicates that EZH2 mutations might contribute to the pathogenesis of specific cases of childhood AML; for example, Ernst et al. detected a somatic, homozygous in-frame 6 bp insertion within EZH2 exon 20 in a 16-year old patient with a 45,X,t(8;21)(q22;q22) karyotype. The gene discussed is EZH2; the disease is acute myeloid leukemia.