Successful nonmyeloablative cord blood transplantation for an infant with malignant infantile osteopetrosis.

Malignant infantile osteopetrosis (MIOP) is a lethal disorder caused by osteoclast dysfunction. The only curative therapy for MIOP is stem cell transplantation (SCT). Because the number of patients is limited, the conditioning regimen and the use of alternative donors for SCT have been controversial and not established. The authors report a case of successful cord blood transplantation (CBT) with a nonmyeloablative regimen (NMR) for MIOP. The patient was a 9-month-old girl with MIOP. Before this diagnosis, she had received chemotherapy under the tentative diagnosis of juvenile myelomonocytic leukemia. She was on mechanical ventilation with tracheotomy due to the progression of MIOP when CBT with NMR was undergone. The conditioning regimen included fludarabine, melphalan, and antithymocyte globulin. Cyclosporine A and methylprednisolone were used for prophylaxis for graft-versus-host disease. Neutrophil engraftment was achieved on day 26 after SCT and has been fully maintained up to the present. Although grade 3 graft-versus-host disease and hepatic veno-occlusive disease occurred, both were controllable. Although the pretransplant condition of our patient was somewhat unusual, this is the first reported case of successful CBT with NMR for MIOP. Because of the urgent need, CBT can be considered as one of the SCT sources for MIOP, especially in a severe, life-threatening setting.