Crohn's disease is a type of inflammatory bowel disease (IBD) that may affect any segment of the gastrointestinal tract. Symptoms often include abdominal pain, diarrhea, fever, abdominal distension, and weight loss. Complications outside of the gastrointestinal tract may include anemia, skin rashes, arthritis, inflammation of the eye, and fatigue. The skin rashes may be due to infections, as well as pyoderma gangrenosum or erythema nodosum. Bowel obstruction may occur as a complication of chronic inflammation, and those with the disease are at much greater risk of colorectal cancer and small bowel cancer.
Although the precise causes of Crohn's disease (CD) are unknown, it is believed to be caused by a combination of environmental, immune, and bacterial factors in genetically susceptible individuals. It results in a chronic inflammatory disorder, in which the body's immune system defends the gastrointestinal tract, possibly targeting microbial antigens. Although Crohn's is an immune-related disease, it does not seem to be an autoimmune disease (the immune system is not triggered by the body itself). The exact underlying immune problem is not clear; however, it may be an immunodeficiency state.