Crohn’s disease is a long-term inflammatory bowel disease (IBD) that causes inflammation in the gastrointestinal (GI) tract. It can affect any part of the GI tract, from your mouth to your anus, but it most commonly impacts the small intestine and the start of the large intestine. Symptoms can range from abdominal pain and diarrhea to weight loss, fatigue, and malnutrition. It’s an autoimmune condition, meaning your immune system mistakenly attacks your own tissues, causing ongoing inflammation.