PROTOCOL OUTLINE: Patients with severe combined immunodeficiency (SCID) using a matched sibling donor receive allogeneic bone marrow or umbilical cord blood transplantation on day 0. Patients receive graft versus host disease (GVHD) prophylaxis with methotrexate IV on days 1, 3, 6, and 11 and cyclosporine IV on days -3 to 50.

Patients with SCID using donors other than histocompatible siblings, Wiskott Aldrich syndrome using a histocompatible sibling donor, Wiskott Aldrich syndrome and under 5 years of age using donors other than histocompatible siblings, X-linked CD40 ligand deficiency using a histocompatible sibling donor, X-linked CD40 ligand deficiency and under 5 years of age using donors other than histocompatible siblings, other primary immunodeficiencies without manifestations of hemophagocytosis using a histocompatible sibling donor, or other primary immunodeficiencies without manifestations of hemophagocytosis and under 5 years of age using donors other than histocompatible siblings receive busulfan IV over 2 hours every 6 hours on days -9 to -6, cyclophosphamide IV on days -5 to -2, and antithymocyte globulin (ATG) twice daily on days -4 to -1. Allogeneic bone marrow or umbilical cord blood transplantation takes place on day 0. Patients receive graft versus host disease (GVHD) prophylaxis with methotrexate IV on days 1, 3, 6, and 11 and cyclosporine IV on days -3 to 50.

Patients with hemophagocytic lymphohistiocytosis, Chediak Higashi syndrome, X-linked lymphoproliferative syndrome, severe progressive Langerhans cell histiocytosis, or other primary immunodeficiencies with complications of hemophagocytosis receive busulfan IV over 2 hours every 6 hours on days -9 to -6, cyclophosphamide IV over 2 hours on days -5 to -2, etoposide IV over 22 hours on days -5 to -3, and ATG IV twice daily on days -2, -1, 1, and 2. Allogeneic bone marrow or umbilical cord blood transplantation takes place on day 0. Patients receive graft versus host disease (GVHD) prophylaxis with methotrexate IV on days 1, 3, 6, and 11 and cyclosporine IV on days -3 to 50.

Patients with Wiskott Aldrich syndrome or other primary immunodeficiencies without manifestations of hemophagocytosis, who are over 5 years of age and using donors other than histocompatible siblings, receive busulfan IV over 2 hours every 6 hours on days -6 and -5, cyclophosphamide IV over 2 hours on days -4 and -3, total body irradiation on day -2, and ATG IV over 2 hours twice daily on days -2, -1, 2, and 3. Allogeneic bone marrow or umbilical cord blood transplantation takes place on days 0 and 1. Patients receive GVHD prophylaxis with methylprednisolone IV every 12 hours on days 2-21, oral prednisone every 12 hours on days 22-100 and then tapered off over days 101 to 128, and cyclosporine IV over 2 hours every 8-12 hours on days -3 to 100.

All patients are followed as determined by their primary physician.