Myelomonocytic differentiation of leukemic blasts accompanied by differentiation syndrome in a case of <i>FLT3</i>-ITD-positive AML treated with gilteritinib

Fms-like tyrosine kinase 3 (FLT3) is one of the most frequently mutated genes in acute myelogenous leukemia (AML) and mutation associated with poor prognosis patients. Two distinct types activating mutations have been identified AML samples. One internal tandem duplications juxtamembrane domain (FLT3-ITD) other point (FLT3-TKD). Gilteritinib a FLT3 inhibitor that inhibits both FLT3-ITD FLT3-TKD. It was reported differentiation leukemic blasts accompanied by syndrome occurs some patients treated gilteritinib. However, information about precise clinical course limited, appropriate management has not established. We report case relapsed Analysis variant allele frequency (VAF) revealed VAF decreased despite achievement complete remission incomplete hematologic recovery. Remarkable increases monocytes granulocytes were observed at 6 months after initiation gilteritinib treatment. Intermittent chemotherapy low-dose cytarabine mitoxantrone effective for reducing myelomonocytosis resolving syndrome.