Reciprocal Clonal Dynamics of Independent FLT3 D835V‐Positive Acute Myeloid Leukemia and Chronic Myeloid Leukemia With Gilteritinib

We report a 65‐year‐old man with FLT3 D835V‐mutated acute myeloid leukemia (AML) and BCR::ABL1 ‐positive chronic myeloid leukemia (CML) that coexisted as genetically independent clones. Cytogenetic and targeted sequencing analyses demonstrated that the AML and CML clones coexisted as distinct entities. During treatment with gilteritinib, the AML blasts regressed, and then the CML clone expanded. Subsequently, the CML burden declined as the AML clone regrew. This case highlights the importance of accurately assessing clonal changes using genetic analysis when implementing molecular targeted therapy for hematologic malignancies.