Inflammatory Bowel Disease

ICD-11: DD70

Disease Overview

Inflammatory bowel disease (IBD) comprises Crohn disease and ulcerative colitis, chronic disorders of the gastrointestinal tract with dysregulated immune response to gut microbiota. Pathophysiology involves barrier dysfunction, innate and adaptive immunity, and microbiome interactions. Heritability ~50–60%; SNP-based h² ~0.25. Over 200 loci identified; key genes include NOD2, IL23R, ATG16L1, and IRGM. Diet, smoking (divergent effects in CD vs UC), antibiotics, and stress modify risk.

Peak onset in late adolescence and early adulthood (15–30). Transition to adult care and adherence are challenges.

Genetic Architecture Summary

GeneVariantGWAS pEvidenceStrength
NOD2rs20668471.0e-50Intracellular bacterial sensing; Crohn-specific0.92
IL23Rrs112090261.0e-40Th17 pathway; shared CD and UC0.88

Heritability

h² SNP: 0.25 — IBD Genetics Consortium (2017)

PRS notes: PRS differentiates CD vs UC; clinical utility under evaluation.

Exposure Modifier Panel

ExposureDirectionStrengthConfidenceMechanism hypothesis
diet-qualityamplify0.65MEDIUM—
tobaccoamplify0.8HIGHSmoking increases Crohn risk; may decrease UC risk

Population Equity Notes

GWAS ancestry breakdown: European-dominated; non-European cohorts growing.

Transferability notes: NOD2 and IL23R replicate; effect sizes vary by ancestry.

Data gaps: African and South Asian GWAS; microbiome G×E.

Tissue Context

intestinal epithelium0.95
lamina propria0.90

Visualizations

Risk Shift by Exposure Stratum

Population-level data only — does not predict individual risk

Tissue Relevance

References

  1. 1.Liu JZ, et al. (2015). Association analyses identify 38 susceptibility loci for inflammatory bowel disease. Nature Genetics. doi:10.1038/ng.3359
  2. 2.Ananthakrishnan AN (2015). Environmental risk factors for inflammatory bowel disease. Gastroenterology. doi:10.1053/j.gastro.2014.07.064