Crohn's disease

Crohn's disease is a chronic inflammatory bowel disease that can affect any part of the gastrointestinal tract from the mouth to the anus, although the ileum, colon and perineum are most commonly involved. It is characterized by transmural granulomatous inflammation. Although the aetiology is unknown, Crohn's disease is thought to result from a complex interplay of multiple genetic and environmental factors. There appears to be an immune dysregulation to microbiota in genetically predisposed individuals. Several genes involved in the interaction between microbiota and the host immune system, in particular the innate immune system, are defective in Crohn's disease, including NOD2 and the autophagy genes ATG16L1 and IRGM. Diarrhoea, abdominal pain, fatigue, weight loss and fever are the hallmarks of Crohn's disease. The clinical features depend on the location and behaviour of the disease in the gastrointestinal tract. Additionally there are extra-intestinal manifestations affecting joints, skin, eyes and the liver. Investigations are directed towards identifying the location, extent, and severity/behaviour (inflammatory, stricturing, penetrating) of disease. The goal of all therapies should be to achieve clinical and endoscopic remission in time to avoid disease progression and surgical resections. Treatment usually features corticosteroids, immunomodulators (thiopurines, methotrexate), anti-tumour necrosis factor-α (TNFα) therapy or surgery. Patients with poor prognostic features may benefit from early treatment with immunomodulator drugs and/or anti-TNFα therapy. Therapeutic drug monitoring can help physicians to improve and personalize the management of Crohn's disease.