Atypical chronic myeloid leukemia achieving good response with azacitidine

The prognosis of atypical chronic myeloid leukemia (aCML) patients is poor, but some patients with a suitable donor can be treated with allogeneic hematopoietic stem cell transplantation (HSCT). However, many of these patients cannot be treated with HSCT due to their age. The effectiveness of decitabine was recently indicated in case reports; however, the effectiveness of azacitidine (AZA) has not yet been reported. We report the case of a aCML patient successfully treated with AZA. A 66-year-old man with no remarkable medical history was admitted to our hospital because of leukocytosis. We diagnosed his disease as aCML and administered hydroxyurea (HU) and AZA. After four courses of AZA, his blood cell values improved, and he no longer needed transfusions and was able to stop HU. He continued receiving AZA without any severe complications. This is the first report that AZA is effective for the treatment of aCML.