In patients with X-linked inhibitor of apoptosis protein (XIAP) deficiency and who are suffering from refractory IBD, HSCT was reported to improve disease symptoms, significantly improve the pediatric ulcerative colitis activity index, and improve gut microbiota dysbiosis observed before treatment such that the microbiota resembled that of healthy family members following HSCT[173]. Here, XIAP is linked to ulcerative colitis.