Several studies have described aberrant DNA methylation in JMML [15,16], but most researchers studied small cohorts, excluding a report of 127 cases of JMML by the European Working Group of MDS (EWOG-MDS) showing that aberrant DNA methylation of four genes (BMP4, CALCA, CDKN2B, and RARB) is associated with poor prognosis [17]. The gene discussed is CDKN2B; the disease is juvenile myelomonocytic leukemia.