Matched unrelated bone marrow transplant for severe combined immunodeficiency.

Severe combined immunodeficiency (SCID) is a lethal disease unless allogeneic bone marrow transplantation (BMT), preferably from a family related HLA identical donor (RID) is given. Previously, some patients received HLA-mismatched related donors (MMRD) BMT, which often resulted in slow immune reconstitution and variable survival. Alternatively, HLA-matched unrelated donors (MUD) BMT have been suggested. Recently, we have directly compared outcome of patients with SCID who received either MMRD or MUD BMT. Survival after MUD BMT was significantly better than after MMRD BMT. Patients who received MUD BMT also had better engraftment of donor cells and immune reconstitution. Recent reports from other centers confirm these results finding that MUD BMT provides excellent survival and better immune reconstitution for patients with SCID. In conclusion, MUD BMT appears vastly superior to MMRD BMT and should be offered as first choice of treatment for patients with SCID when RID is unavailable.