Allogeneic hematopoietic stem cell transplantation (HSCT) is a possibly curative therapy for Wiskott-Aldrich syndrome patients (WAS). In terms of overall survival, reported HSCT results have improved over time, however, some studies have identified older age and HSCT from alternate donors as risk factors for inferior outcomes. For a study, researchers looked at 197 patients who underwent conditioning as suggested by the Inborn Errors Working Party (IEWP) between 2006 and 2017 at European Society for Blood and Marrow Transplantation centers: either busulfan (n=103) or treosulfan (n=94) combination with fludarabine thiotepa. After a median of 44.9 months of post-HSCT follow-up, 176 patients remained alive, resulting in a 3-year overall survival rate of 88.7% and chronic graft-versus-host disease (GVHD)-a free survival rate of 81.7% (events include death, graft failure, and severe chronic GVHD). 

Overall survival and chronic GVHD-free survival were not impacted by conditioning regimen (busulfan vs treosulfan), donor type (matched sibling donor/matched family donor vs matched unrelated donor/mismatched unrelated donor vs mismatched family donor), or HSCT time (2006-2013 vs 2014-2017). Patients undergoing HSCT who were 5 years old showed considerably improved overall survival. The cumulative occurrences of grade III to IV acute GVHD and extensive/moderate/severe chronic GVHD were 6.6 and 2.1%, respectively. Patients who received treosulfan-based conditioning had a greater rate of graft failure and mixed donor chimerism, as well as a higher frequency of subsequent surgeries (second HSCT, unconditioned stem cell boost, donor lymphocyte infusion, or splenectomy). In conclusion, HSCT for WAS with current IEWP conditioning regimens led to excellent survival and low rates of GVHD, independent of donor or stem cell source, but age 5 years remained a risk factor for overall survival.