Rationale: Chemotherapy administration before a donor stem cell transplant is necessary to stop the patient's immune system from rejecting the donor's stem cells. When healthy stem cells from a donor are infused into the patient, the donor white blood cells can provide the missing enzyme that causes the metabolic disease. Sometimes the transplanted cells from a donor can make an immune response against the body's normal cells. Giving a monoclonal antibody, alemtuzumab, before transplant and cyclosporine and mycophenolate mofetil before and after transplant may stop this from happening. This may be an effective treatment for inherited metabolic disorders.