 We herein present a case of pediatric therapy-related myelodysplastic syndrome (t-MDS) with complex karyotype who was treated with azacitidine (AZA) for AML1-EVI1 fusion transcript as minimal residual disease after allogeneic hematopoietic stem cell transplantation (HSCT).     ///    "After 9 cycles of AZA, the AML1-EVI1 fusion transcript disappeared, and there was no manifestation of graft versus host disease during AZA treatment. "