Crohn’s disease and ulcerative colitis, affect as many as 1.6 million Americans, most of whom are diagnosed before age 35. These chronic, life-long conditions can be treated but not cured. IBD can significantly affect a patient’s quality of life and may have a high financial burden. By generating greater awareness of Crohn’s disease and ulcerative colitis, the Crohn’s & Colitis Foundation of America (CCFA) believes that more progress can be made toward finding a cure and reducing the significant impact of these diseases on individuals and the US healthcare system. CCFA is pleased to provide this Fact Book, which compiles important statistics and information and offers a brief overview of IBD. This Fact Book will be of use to patients and their families, as well as physicians and others with an interest in broadening their knowledge of IBD. Introduction 4 Crohn’s disease and ulcerative colitis are inflammatory bowel diseases that cause chronic inflammation and damage in the gastrointestinal (GI) tract (Figure 1). The GI tract is responsible for digestion of food, absorption of nutrients, and elimination of waste. Inflammation impairs the ability of affected GI organs to function properly, leading to symptoms such as persistent diarrhea, abdominal pain, rectal bleeding, weight loss and fatigue. While ongoing inflammation in the GI tract occurs in both Crohn’s disease and ulcerative colitis, there are important differences between the two diseases. Crohn’s Disease Crohn’s disease can affect any part of the GI tract, from the mouth to the anus. It most commonly affects the end of the small intestine (the ileum) where it joins the beginning of the colon. Crohn’s disease may appear in “patches,” affecting some areas of the GI tract while leaving other sections completely untouched. In Crohn’s disease, the inflammation may extend through the entire thickness of the bowel wall. Ulcerative Colitis Ulcerative colitis is limited to the large intestine (colon) and the rectum. The inflammation occurs only in the innermost layer of the lining of the intestine. It usually begins in the rectum and lower colon, but may also spread continuously to involve the entire colon. Indeterminate Colitis In some individuals, it is difficult to determine whether their IBD is Crohn’s disease or ulcerative colitis. In these rare cases, people are given the diagnosis of indeterminate colitis (IC). Cause While the exact cause of IBD is not entirely understood, it is known to involve an interaction between genes, the immune system, and environmental factors (Figure 2). The immune system usually attacks and kills foreign invaders, such as bacteria, viruses, fungi, and other microorganisms. However, in people with IBD, the immune system mounts an inappropriate response to the intestinal tract, resulting in inflammation. This abnormal immune system reaction occurs in people who have inherited genes that make them susceptible to IBD. Unidentified environmental factors serve as the “trigger” that initiates the harmful immune response in the intestines. Historical Perspective and Research Advances Ulcerative colitis was first described in 1875 by two English physicians, Wilks and Moxon, who distinguished it from diarrheal diseases caused by infectious agents. Reports of a disease with similar symptoms to ulcerative colitis date back to before the Civil War and even many years before that, although it was not named as a distinct disease until 1875. Crohn’s disease was first described in 1932 by three doctors—Burrill Crohn, Leon Ginzberg, and Gordon D. Oppenheimer. At the time, any disease in the small intestine was thought to be intestinal tuberculosis. These doctors collected data from 14 patients with symptoms of abdominal cramps, diarrhea, fever, and weight loss, which showed that the symptoms were not the result of tuberculosis or any other known disease. They described a new disease entity, which was first called regional ileitis, and later, Crohn’s disease. In the years since inflammatory bowel diseases were identified, major scientific advances, specifically in the fields of genetics, immunology, and microbiology, have led to greater understanding of the underlying mechanisms involved in IBD, resulting in the development of