Bridging therapy by azacitidine in a patient with atypical chronic myeloid leukemia, followed by human leukocyte antigen- haploidentical stem cell transplantation

Abstract

Atypical chronic myeloid leukemia(aCML)is rare, with a poor prognosis. A 30-year-old man with aCML was referred to our hospital for allogeneic hematopoietic stem cell transplantation. Even after administering hydroxyurea, the neutrophil counts and level of lactate dehydrogenase(LDH)in the peripheral blood was high. On referral, a bone marrow aspirate smear revealed hypercellularity with granulocytic proliferation and granulocytic dysplasia. After administration of azacitidine, the neutrophil counts and LDH level in peripheral blood decreased. The patient underwent peripheral blood stem cell transplantation from a human leukocyte antigen(HLA)haplo-matched related donor, on day 24 of azacitidine administration. He achieved neutrophil engraftment on day 17 following transplantation. A chimerism test of bone marrow showed mixed chimera on day 21 and 49 following transplantation; however, complete donor type was observed on day 81, 179 and 326 following transplantation. In cases of aCML diagnosis, prompt preparation for transplantation is advised. Further studies in a larger sample of patients with aCML are necessary to determine the suitable donor source and the efficacy of azacitidine as a bridging therapy for transplantation. (Japanese Journal of Transplantation and Cellular Therapy 10 (4) : 183-189, 2021.