First Report of Hematopoietic Stem Cell Transplantation for Children Diagnosed with Wiskott-Aldrich Syndrome in Vietnam.

Background: Awareness of inborn error immunity, such as Wiskott-Aldrich syndrome (WAS), is still lacking in Vietnam. The shortage of clinical immunologists and transplantation teams lead to poor prognosis for patients. Objective: Describe initial data about hematopoietic stem cell transplantation (HSCT) for WAS. Methods: Retrospective analyzing 15 procedures on 13 patients at the Vietnam National Children's Hospital from 2020 to 2024. Results: The median age at HSCT was 34 months (range: 17-86). Of the patients, 73.3% received myeloablative conditioning based on busulfan, while 26.7% underwent reduced-intensity conditioning. Donor sources included matched sibling donors (MSD, 20.0%), unrelated cord blood (UCB, 33.3%), phenotypically identical family donor (MFD, 6.7%), and mismatched related donors (MMRD, 40.0%). The median stem cell dose was 4.9 × 10^6/kg of the recipient's body weight (range: 0.33 to 10.4 × 10^6/kg). Neutrophil and platelet engraftment occurred at a median of 14 days (range: 10-19) and 48 days (range: 14-143), respectively. By day +30, 73.3% of patients achieved full donor chimerism. One patient experienced graft failure, and another faced graft rejection two months post-transplant, both of whom underwent a second transplant with different donors. The overall survival rate was 92.3% with a median follow-up of 23 months (range: 6-53), with one patient died from chronic graft-versus-host disease (cGVHD). All surviving patients achieved normalization of platelet counts. Conclusion: HSCT offers significant benefits to WAS patients, achieving an excellent overall survival rate.