Analysis of Genes Associated With Monogenic Primary Immunodeficiency Identifies Rare Variants in XIAP in Patients With Crohn's Disease.

BACKGROUND & AIMS: A few rare monogenic primary immunodeficiencies (PIDs) are characterized by chronic intestinal inflammation that resembles Crohn's disease (CD). We investigated whether 23 genes associated with 10 of these monogenic disorders contain common, low-frequency, or rare variants that increase risk for CD. METHODS: Common and low frequency variants in 1 Mb loci centered on the candidate genes were analyzed using meta-data corresponding to genotypes of approximately 17,000 patients with CD or without CD (controls) in Europe. The contribution of rare variants was assessed by high-throughput sequencing of 4750 individuals, including 660 early-onset and/or familial cases among the 2390 patients with CD. Variants were expressed from vectors in SW480 or HeLa cells and functions of their products were analyzed in immunofluorescence, luciferase, immunoprecipitation, and immunoblot assays. RESULTS: We reproduced the association of the interleukin 10 locus with CD (P = .007), although none of the significantly associated variants modified the coding sequence of interleukin 10. We found XIAP to be significantly enriched for rare coding mutations in patients with CD vs controls (P = .02). We identified 4 previously unreported missense variants associated with CD. Variants in XIAP cause the PID X-linked lymphoproliferative disease type 2, yet none of the carriers of these variants had all the clinical features of X-linked lymphoproliferative disease type 2. Identified XIAP variants S123N, R233Q, and P257A were associated with an impaired activation of NOD2 signaling after muramyl dipeptide stimulation. CONCLUSIONS: In a systematic analysis of variants in 23 PID-associated genes, we confirmed the association of variants in XIAP with CD. Further screenings for CD-associated variants and analyses of their functions could increase our understanding of the relationship between PID-associated genes and CD pathogenesis.

Long-term Outcomes with Anti-TNF Therapy and Accelerated Step-up in the Prospective Pediatric Belgian Crohn's Disease Registry (BELCRO).

BACKGROUND: Accelerated step-up or anti-tumor necrosis factor (TNF) before first remission is currently not recommended in pediatric Crohn's disease. METHODS: Five-year follow-up data from a prospective observational cohort of children diagnosed with Crohn's disease in Belgium were analyzed. Disease severity was scored as inactive, mild, or moderate to severe. Remission or inactive disease was defined as sustained if lasting ≥2 years. Univariate analyses were performed between anti-TNF-exposed versus naive patients and anti-TNF before versus after first remission and correlations assessed with primary outcomes average disease severity and sustained remission. RESULTS: A total of 91 patients (median [IQR] age 12.7 [10.9-14.8] yrs, 53% male) were included. Disease location was 12% L1, 23% L2, and 64% L3 with 76% upper gastrointestinal and 30% perianal involvement. Disease severity was 25% mild and 75% moderate to severe. Of 66 (73%) anti-TNF-exposed patients, 34 (52%) had accelerated step-up. Anti-TNF use was associated with age (13.1 [11.5-15.2] versus 11.8 [8.7-13.8] yrs; P < 0.05), L2 (29% versus 8%; P = 0.04), and average disease severity (1.7 [1.4-1.9] versus 1.4 [1.3-1.6]; P < 0.001). Duration of anti-TNF correlated with average disease severity (r = 0.32, P = 0.002). Accelerated step-up was also associated with age (13.3 [12.1-15.9] versus 12.5 [10.2-14.1]; P = 0.02) and average disease severity (1.8 [1.6-1.9] versus 1.6 [1.3-1.8]; P = 0.002). Duration of sustained remission was similar in all patients, and no serious infections, cancer, or deaths were reported. CONCLUSIONS: Anti-TNF therapy and accelerated step-up in older patients with more severe disease leads to beneficial long-term outcomes.