Late hematological improvement of myelodysplastic syndrome following treatment with 5-azacitidine therapy.

Recently, 5-azacitidine has been reported to improve the survival of patients with high-risk myelodysplastic syndrome (MDS) and was approved for the treatment of MDS in Japan. We herein report a case of high-risk MDS in which the patient exhibited a hematological improvement three months after the first cycle of 5-azacitidine therapy. The second cycle of 5-azacitidine was not administered due to a severe pulmonary infection. Bone marrow aspiration revealed a decrease in the level of blast cells from 7.0% to 0.7%, and the subclassification of MDS improved from refractory anemia with excess blasts (RAEB)-1 to refractory cytopenia with unilineage dysplasia. This case demonstrates a possible late effect of 5-azacitidine treatment.