In a nationwide survey conducted by our department, of 225 cases of VEO-IBD that developed before the age of 6, 26 cases (11.6%) were found to have monogenic IBD associated with primary immunodeficiencies such as chronic granulomatous disease, IL-10 receptor abnormality, A20/TNFAIP3 gene abnormality, and XIAP deficiency (Table 3)35). Here, XIAP is linked to inflammatory bowel disease.