Consequences of identifying XIAP deficiency in an adult patient with inflammatory bowel disease

In some patients with extreme phenotypes of inflammatory bowel disease (IBD; in particular in those with infantile or very early onset IBD with <6 years of onset, nonresponsiveness to therapy, or extraintestinal manifestations), Mendelian forms of IBD have been described.1 To identify patients with Mendelian disease-associated IBD in a cohort with age at diagnosis between 7 and 40 years of age, we screened for 59 Mendelian forms of IBD by exome sequencing across 503 patients with IBD with severe disease, as indicated by need for intestinal surgery and/or therapy progression to biologics (Supplementary Material). This enriched the group of patients toward those with a diagnosis of Crohn’s disease: 73% Crohn’s disease and 26% ulcerative colitis, 1% IBD unclassified. Owing to the selection criteria, rates of surgery and exposure to biological anti-tumor necrosis factor therapy (in particular adalimumab and infliximab) were higher compared with the overall Oxford IBD cohort (67% vs 26% and 74% vs 27%, respectively; P < .05), reflecting an enrichment of patients with acute severe ulcerative colitis (30% of patients with ulcerative colitis) or Crohn’s-associated fistulizing disease, abscesses, or strictures.