Crohn's Disease

Crohn's disease is defined by where and how deep the inflammation goes

Crohn's is an inappropriate, chronic T-cell-driven immune response against the gut (in a genetically susceptible person, likely triggered by an altered response to luminal bacteria) that can affect any part of the gastrointestinal tract from mouth to anus, characteristically with skip lesions (patches of diseased bowel separated by normal mucosa) most often in the terminal ileum and colon. Critically, the inflammation is transmural, extending through the full thickness of the bowel wall rather than staying confined to the mucosa. Almost every distinctive feature of Crohn's (its complications, its imaging appearance, its surgical behaviour) follows from this single fact of full-thickness, patchy involvement.