PRETRANSPLANT CONDITIONING WITH BUSULFAN (MYLERAN) AND CYCLOPHOSPHAMIDE FOR NONMALIGNANT DISEASES

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Abstract
Four pediatric patients with diseases potentially curable by bone marrow transplantation (BMT), i.e., common variable immune deficiency, Wiskott-Aldrich Syndrome (WAS), mucopolysaccharidosis type VI, and mucopolysaccharidosis type I, received a conditioning regimen consisting of busulfan and cyclophosphamide prior to BMT from HLA-identical, mixed leukocyte culture (MLC)-unreactive siblings. Only 1 of the 4 patients achieved full engraftment. Of the remaining 3 patients, 1 experienced failure of engraftment, and 2 had persistent mixed chimerism. Although no serious complications were directly related to the preparative therapy, the doses of busulfan and cyclophosphamide previously described to be adequate for conditioning children with WAS were completely effective in only 1 of 3 pediatric patients in this series. Despite a higher hose of busulfan (16 mg/kg), mixed chimerism was observed in a subsequent patient. Of 13 evaluable patients in the literature in whom busulfan and cyclophosphamide had been used as preconditioning regimens for a variety of nonmalignant conditions 8 demonstrated lack of complete and sustained engraftment although clinical improvement accompanied partial engraftment in some cases. Additional immunosuppressive and/or myeloablative conditioning is necessary if complete engraftment is attempted in histocompatible allogeneic BMT for many of the nonmalignant disorders.