Crohn's disease
Crohn's disease is a long-term inflammatory bowel disease that can inflame any part of the digestive tract, from the mouth to the anus, though it most often affects the end of the small intestine. The inflammation can reach through the full thickness of the bowel wall and tends to appear in patches, with healthy tissue in between.
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Crohn's disease is one of the two main forms of inflammatory bowel disease (IBD). It is a long-term condition where part of the gut becomes inflamed, and unlike ulcerative colitis it can affect any part of the digestive system, from the mouth to the anus. Most often it settles where the end of the small intestine meets the large intestine (NHS; Cleveland Clinic).
Two features mark it out from ulcerative colitis. The inflammation can reach through the full thickness of the bowel wall, not just the inner lining, and it tends to appear in patches, with stretches of healthy tissue in between (Crohn's & Colitis Foundation).
Main symptoms
Common symptoms are diarrhoea, blood or mucus in your poo, stomach pain or cramps, and feeling very tired or generally unwell. Loss of appetite and weight loss are common, and some people also have sore joints, sore eyes or skin rashes (NHS).
A relapsing pattern
Like ulcerative colitis, Crohn's disease tends to come and go in cycles: quieter spells with few or no symptoms, called remission, and times when symptoms return and flare up. It cannot currently be cured, but treatments can help prevent and manage symptoms (NHS; Cleveland Clinic).
What causes it
Symptoms are caused by a problem with the immune system, which attacks part of the gut. It is not fully understood why this happens, but a combination of the immune system, a person's genes and environmental factors is thought to be involved (NHS; Cleveland Clinic).