Successful treatment of relapsed FLT3-mutated donor cell-derived MDS/AML with FLT3 inhibitor gilteritinib.

Donor cell-derived myelodysplastic syndrome/acute myeloid leukemia is a rare but serious complication of allogeneic hematopoietic stem cell transplantation, and its optimal treatment has not been established. Here, we report a case of a 44-year-old woman who was diagnosed with donor cell-derived myelodysplastic syndromes with excess blasts carrying RAD21 and KMT2D mutations after six-year clinical remission of her initial acute myeloid leukemia treated with bone marrow transplantation from an unrelated male donor. The disease subsequently transformed to acute myeloid leukemia harboring a newly acquired FLT3 internal tandem duplication mutation. Azacitidine and venetoclax with cytarabine were both ineffective, but gilteritinib monotherapy rapidly reduced blasts and achieved near complete remission. The patient then underwent haploidentical stem cell transplantation from her son, followed by gilteritinib maintenance therapy. She achieved complete remission with clearance of donor cell-derived mutations and has remained in remission for more than one year. To our knowledge, this is the first case report of a relapsed FLT3-mutated donor cell-derived acute myeloid leukemia who was successfully treated with a FLT3 inhibitor, gilteritinib, which highlights the potential effectiveness of gilteritinib not only as a salvage therapy but also as an effective bridging and maintenance therapy in relapsed FLT3-mutated donor cell-derived acute myeloid leukemia.