In addition to the detection of TET2 mutations that pre-date full-blown malignancies, recent studies have highlighted preleukemic phases in AML that are associated with mutations in other genes affecting DNA methylation, such as DNMT3A, IDH1 and IDH2 [122], and in genes involved in chromatin structure, such as SMC1A (structural maintenance of chromosome 1A) [123]. The gene discussed is IDH2; the disease is acute myeloid leukemia.