Abstract
Allogeneic hematopoietic stem cell transplantation (allo-HSCT) for inborn errors of immunity (IEI) has traditionally relied on myeloablative conditioning (MAC), although its substantial toxicity has limited its use. Reduced-intensity conditioning (RIC) has decreased treatment-related mortality; however, it is associated with an increased risk of graft failure. More recently, dose-adjusted busulfan-based conditioning has demonstrated favorable outcomes in patients with IEI. At our institution, a high-dose melphalan–based regimen (FLU/MEL 180) has been implemented as an alternative approach. This retrospective study evaluated 25 allo-HSCT procedures performed between 2005 and 2023 for patients with nonmalignant hematological disorders, primarily IEI, excluding bone marrow failure. Engraftment failure occurred in five transplantations, all within the RIC group, whereas no failures were observed in the MAC or FLU/MEL 180 groups. These findings suggest that high-dose melphalan conditioning may reduce the risk of engraftment failure and represents a viable option for patients with IEI, particularly in settings where pharmacokinetic monitoring of busulfan is not feasible.
