An 80-year-old man was admitted to our hospital because of pancytopenia. Bone marrow examination revealed an increase in the number of dysplastic cells indicating trilineage dysplasia. A 5q13q31 deletion was the only genetic abnormality found, and consequently, 5q deletion syndrome was diagnosed. Although lenalidomide therapy was initiated, it had to be discontinued because of Stevens-Johnson syndrome, which occurred during the second course of treatment. There was no discernible hematological improvement, and bone marrow aspiration showed transformation to refractory anemia with excess blasts-2(RAEB-2)after lenalidomide therapy. However, by changing the therapy to azacitidine, cytogenetic remission was achieved.