Dynamics of DNA methylation, mutant alleles as neoplastic clone markers, and peripheral blood counts. We analyzed methylation of 10 genes at baseline in all 3 patients, and genes with increased baseline methylation were followed during and after the treatment. Patient 1: CMML with JAK2 mutation of 49% alleles before treatment, which decreased to undetectable level after 4 cycles of decitabine. CDH13 methylation was present at initiation of therapy and decreased after decitabine. Patient 2: CMML with NPM1 mutation of 35% alleles before treatment, which decreased to undetectable levels after 4 cycles. PGRB methylation followed the dynamics of LINE1 methylation after decitabine. Patient 3: CMML with JAK2 mutation of 35% alleles before treatment, which decreased to 6% after 2 cycles of decitabine and then increased again. CDH1, CDH13, and NPM2 methylation was present at initiation of therapy and decreased after decitabine. Cycles of decitabine treatment are indicated as purple rectangles above the graphs.