All patients receive a conditioning regimen comprising fludarabine IV on day -6, cyclophosphamide IV on days -5 and -4, anti-thymocyte globulin IV on days -4 and -2, and total body irradiation on days -3 to 0. Patients also receive methylprednisolone IV every 12 hours for 4 doses on days -2 to 0. Tacrolimus IV is administered continuously on day -1 and continues either orally or IV for 6 months. Bone marrow is infused on day 0. Filgrastim (G-CSF) is administered subcutaneously from day 0 until blood counts recover.