Acute Myeloid Leukemia with an FMS-like Tyrosine Kinase 3-tyrosine Kinase Domain Mutation Developing Gilteritinib-induced Differentiation Syndrome.

FMS-like tyrosine kinase 3 (FLT3) mutations are observed in 30% of acute myeloid leukemia (AML) cases and indicate a poor prognosis. FLT3 inhibitors, such as gilteritinib, improve outcomes but may cause differentiation syndrome (DS) in approximately 3% of patients. We herein report a case of FLT3-tyrosine kinase domain-mutated AML treated with idarubicin and cytarabine, followed by a single dose of gilteritinib. The patient developed DS that required intubation. Initial steroid therapy was ineffective; however, steroid pulse therapy and additional idarubicin resolved the DS. This case shows that gilteritinib-induced DS can occur early and severely and requires prompt and aggressive management.