Advances in Our Understanding of the Pathogenesis of Inflammatory Bowel Disease

The pathogenesis of inflammatory bowel disease (IBD) is complex and likely multifactorial. Our understanding has evolved in recent years, and both Crohn’s disease (CD) and ulcerative colitis (UC) are deemed to be immunologically mediated chronic inflammatory diseases that develop in a genetically susceptible individual. Large genome-wide association studies have unraveled multiple pathways involved in IBD pathogenesis, and as of now, more than 200 IBD susceptibility loci have been identified. It has also become clear that genetics does not explain the entire story and that environmental factors and gut dysbiosis play a significant role in IBD pathogenesis. The complex multidirectional interactions between the gut microbiome, altered immune environment, lifestyle, pharmacological agents, and infections are among the possible contributors. In this chapter, we will explore the knowns and unknowns of IBD pathogenesis.