Adults age ≥ 18 years with CD34+ MDS or AML undergoing allo-HSCT. If donor CD34+ chimerism < 80%, offered azacitidine. Morphologic relapse (i.e. BM blasts ≥ 5%) around the time of chimerism drop and organ impairment (hepatic, renal) were excluded. This evidence concerns the gene CD34 and acute myeloid leukemia.