Bone Marrow Features in Patients With Acute Myeloid Leukemia Treated With Novel Targeted Isocitrate Dehydrogenase 1/2 Inhibitors

This case report aimed to review the bone marrow features of patients with acute myeloid leukemia (AML) treated with isocitrate dehydrogenase 1/2 (IDH1/2) inhibitors. Five patients with AML treated with an IDH1/2 inhibitor were identified and retrospectively reviewed. We described the morphologic and immunophenotypic findings in the bone marrow, as well as ancillary study results. Two patients showed a hypercellular bone marrow with morphologic and immunophenotypic differentiation of blasts. The bone marrow of one patient displayed a hypoplastic phase. Four of the five patients demonstrated unusual morphologic and/or immunophenotypic populations, including basophilia with mild alterations on the myeloid blasts, a small subset of blasts with expression of T-cell markers not seen in the original immunophenotype, a cluster of differentiation 117 (CD117)-positive progenitor population with erythroid differentiation, and another population reminiscent of erythroid differentiation. Unusual morphologic and immunophenotypic populations can be seen in the bone marrows of patients treated with IDH1/2 inhibitors in the presence or absence of definite residual disease. The significance of these populations is uncertain, but further studies could be helpful to understand the meaning of these findings.