Crohn's disease is a chronic inflammatory disease of the gastrointestinal tract, but can affect any area of the digestive tract from the mouth to the anus. The symptoms vary greatly according the affected area, but the main ones are abdominal pain, diarrhea, fever and weight loss. It can also cause skin lesions, anal abscesses, fissures, joint pain and anal pain. The exact cause of Crohn's disease is still unknown although recent studies point to a problem in the immune system or a bacterial cause. The disease is not contagious, but is genetically-inherited tendency.