Successful Engraftment After Repeat Cord Blood Transplantation Using an Identical Conditioning Regimen for MPS II

Graft failure remains a major complication in cord blood transplantation (CBT), particularly in patients with nonmalignant diseases, such as inherited metabolic disorders. However, optimal strategies for retransplantation after graft failure remain controversial. Here, we describe a case of mucopolysaccharidosis type II (MPS II) in which durable engraftment was successfully achieved following a second CBT using the same conditioning regimen as the initial transplantation. A 4-year-old boy with MPS II underwent unrelated CBT after undergoing a reduced-intensity conditioning regimen consisting of total abdominal irradiation, fludarabine, and melphalan. He acquired methicillin-resistant Staphylococcus aureus-associated sepsis early in the posttransplant period and developed graft failure on day 28, presumably due to drug-induced myelosuppression rather than insufficient conditioning intensity. Sixty-six days after the first transplantation, a second CBT was performed using the identical conditioning backbone but with antithymocyte globulin as immunosuppressant. The second course was complicated by severe hypercytokinemia with hemophagocytosis, cytomegalovirus antigenemia requiring preemptive antiviral therapy, and upper gastrointestinal bleeding. Nevertheless, donor chimerism remained high, and engraftment was confirmed on day 40 with transfusion independence on day 50. This case highlights the need for an etiological assessment of graft failure and demonstrates the viability of the initial conditioning regimen as a retransplantation strategy when inadequate conditioning is unlikely.