In terms of allo-HSCT for XIAP deficiency, Marsh et al. described the international experience in 19 patients showing an extremely high transplant-related mortality in those prepared with an MAC (7/8 patients died), in comparison with those receiving a reduced-intensity conditioning (RIC) (5/11 patients died) (32). The gene discussed is XIAP; the disease is hyperinsulinemic hypoglycemia, familial, 4.