Abstract: Objective To investigate the effect of haploidentical hematopoietic stem cell transplantation and mesenchymal stem cell infusion in the treatment of metachromatic leukodystrophy.Methods A 7-year-old girl with metachromatic leukodystrophy received hematopoietic stem cell transplantation and mesenchymal stem cells infusion.The pretreatment regimen consisted of fludarabine,cyclophosphamide,and busulfan.The prophylaxis of acute graft-versus-host disease was performed by the administration of anti-CD25 monoclonal antibody,cyclosporine A,methotrexate,mycophenolate mofetil,anti-thymocyte globulin and G-CSF-mobilized bone marrow.After hematopoietic reconstruction,mesenchymal stem cells derived from umbilical cord were intravenously infused once a week for 4 consecutive weeks.Results The patient achieved rapid hematopoietic engraftment of donor origin.Neutrophil（> 0.5 × 109 / L） and platelet（> 20 × 109 / L） recovery was achieved on +11 day.On day 14,arylsulfatase A level in peripheral blood leukocytes was significantly increased and it reached to the normal range on +28 day.No acute graft-versus-host disease was observed.One month after transplantation,finger-printing analysis indicated an achievement of complete donor-type hematopoiesis.Neurological symptoms gradually recovered.Conclusion Haploidentical hematopoietic stem cell transplantation and mesenchymal stem cell infusion for the treatment of metachromatic leukodystrophy were safe,effective and leukocyte arylsulfatase A level rises rapidly.The novel regimen described here might be one of the options patients with metachromatic leukodystrophy and lack of HLA-matched sources.

Key words: Hematopoietic stem cell transplantation, Haploidentical, Mesenchymal stem cells, Metachromatic leukodystrophy