Successful Allogeneic Hematopoietic Stem Cell Transplantation in XIAP Deficiency Using Reduced-Intensity Conditioning

Hematopoietic stem cell transplantation (HSCT) is currently the only available curative therapy for X-linked inhibitor of apoptosis (XIAP) deficiency. Myeloablative conditioning regimens are associated with high mortality rates. Reduced-intensity conditioning (RIC) is recommended in order to decrease treatment-related toxicities, but RIC regimens increase the risk for mixed donor-recipient chimerism that may progress to graft loss. We report our experience with a patient with XIAP deficiency who was successfully treated with allogeneic HSCT using a RIC protocol. Post-transplant chimerism was vigilantly monitored and maintained with donor lymphocyte infusions and a stem cell boost to a level that prevented hemophagocytic lymphohistiocytosis recurrence.