A rare KMT2A::CBL transcript in an acute monoblastic leukemia patient with an unfavorable outcome

Lysine [K] methyltransferase 2A (KMT2A, previously known as MLL) gene rearrangements are common in acute leukemias of various lineages and are associated with features such as chemotherapy resistance and rapid relapse. KMT2A::CBL is a rare fusion of unknown pathogenesis generated by a unique interstitial deletion of chromosome 11 that has been reported across a wide age range in both acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) patients. The leukemogenic effect of the KMT2A::CBL rearrangement and its association with clinical prognosis have not been well clarified. We report the case of a 64-year-old female who was diagnosed with acute monoblastic leukemia (M5a) and who acquired the rare KMT2A::CBL fusion. The patient received multiple cycles of therapy but did not achieve remission and eventually succumbed to severe infection and disease progression. Additionally, we characterized the predicted KMT2A-CBL protein structure in this case to reveal the underlying leukemogenic mechanisms and summarized reported cases of hematological malignancies with KMT2A::CBL fusion to investigate the correlation of gene rearrangements with clinical outcomes. This report provides novel insights into the leukemogenic potential of the KMT2A::CBL rearrangement and the correlation between gene rearrangements and clinical outcomes.