ABSTRACT
Outcomes are extremely poor in Down syndrome-associated acute lymphocytic leukemia, particularly in recurrent cases. A 2-year-old boy with Down syndrome-associated acute lymphocytic leukemia achieved complete remission after standard chemotherapy. However, he experienced recurrence twice in the bone marrow and central nervous system. Salvage treatments included whole-brain/whole-spine irradiation. Thereafter, the patient received a second cord blood transplantation after the reduced-intensity conditioning. The graft was characterized by killer cell immunoglobulin-like receptor ligands mismatch. The patient has subsequently survived for 6.5 years without recurrence. We speculate that killer cell immunoglobulin-like receptor ligand-mismatched cord blood transplantation enhanced the graft-versus-leukemia effect through natural killer cells, and conferred long-term remission.