I. Determine safety of nonmyeloablative conditioning and hematopoietic cell transplantation (HCT) from human leukocyte antigen (HLA)-haploidentical related donors for patients with nonmalignant inherited disorders who do not have an HLA-matched related or unrelated donor.
I. Determine whether nonmyeloablative conditioning and HCT from an HLA-haploidentical related donor graft can establish mixed chimerism (> 5% cluster of differentiation [CD]3+ donor T-cell chimerism) in patients with nonmalignant inherited disorders.
II. Transplant related mortality at day 100.
III. Incidence and severity of graft-versus-host disease (GHVD).
IV. Immune reconstitution.
V. Infections during the first 200 days after HCT.
NONMYELOABLATIVE CONDITIONING REGIMEN: Patients receive fludarabine phosphate intravenously (IV) over 1 hour on days -6 to -2; cyclophosphamide IV over 1 hour on days -6 and -5; and undergo total body irradiation on day -1.
TRANSPLANTATION: Patients undergo allogeneic bone marrow transplant on day 0.
POST-TRANSPLANT IMMUNOSUPPRESSION: Patients receive cyclophosphamide IV over 1 hour on days 3 and 4, and mycophenolate mofetil orally (PO) every 8 hours on days 5-30 then twice daily (BID) to day 40, and then if there is no evidence of active GVHD and donor engraftment is > 95% (or by Principal Investigator [PI] approval) taper until approximately day 96, or faster at discretion of PI. Patients also receive tacrolimus IV continuously over 22-24 hours starting on day 5 post-transplant and continue on tacrolimus through day 100 followed by a taper to approximately day 180 if there is no evidence of GVHD and their graft is doing well. Patients may convert to oral tacrolimus given BID or three times daily (TID) when the patient is able to take medications orally and has a therapeutic drug level. In addition, patients will receive sirolimus orally beginning on day 5 through day 180 followed by a taper to approximately day 210 if there is no evidence of GVHD and their graft is doing well.
After completion of study treatment, patients are followed up at 6, 12, 18, and 24 months, and then annually thereafter for 5 years.