RÉSUMÉ
We described the successful allogeneic matched sibling bone marrow transplantation (BMT) in a 5-year-old Thai boy in whom osteopetrosis was diagnosed on the basis of anemia, thrombocytopenia, leukoerythroblastosis, sclerotic bone, hepatosplenomegaly, and visual deficit from an encroachment of cranial nerve foramina. The preparative regimen included 4 days of busulfan 4 mg/kg/day, and 4 days of cyclophosphamide 50 mg/kg/day. Complete hematopoietic engraftment and no evidence of graft versus host disease were shown after BMT. Complete hematologic findings were corrected. His hematopoietic chimerism was changed to that of his donor. Post BMT, he has no hepatosplenomegaly. His bone radiographic findings revealed normal after BMT. Bone marrow biopsy showed normalized bone and bone marrow matrix. However, his vision remained impaired. We believe that this is the first case of successful bone marrow transplantation in an osteopetrosis patient in Thailand.