Crohn’s disease is an inflammatory bowel disease of unknown aetiology. However, it shares many features with the autoinflammatory diseases,and some cases are known to be associated with mutations in the gene NOD2 that controls inflammatory responses to bacteria. Mutations cause failure of the formation of the mucin and antimicrobial barrier lining the bowel and may also inhibit degradation of bacteria. Changes in bowel flora are probably also important.Granulomatous inflammation affects the ileocaecal region, causing thickening and ulceration. Symptoms vary with the severity of the disease, but effects can include abdominal pain, variable constipation or diarrhoea and, sometimes, obstruction and malabsorption. Repeated bowel resections may ultimately be needed. Many other sites can be affected including any part of the bowel, joints and skin.
Treatment controls symptoms but is not curative. Dietary adjustment, corticosteroids, antibiotics, sulfasalazine or mesalazine, immunosuppressants and tumour necrosis factor (TNF)-alpha blockers (e.g. infliximab) are used.