Crohn's disease, also called enteritis or ileitis, causes swelling and inflammation of the lining of the digestive or gastrointestinal (GI) tract. The swelling affects all of the tissue layers of the intestines, causing pain and frequent diarrhea. Although scientists are not sure exactly what causes Crohn's disease, they theorize that the environment, genetics and a malfunction of the body's immune system each plays a role.
Description
Crohn's disease is a type of inflammatory bowel disease. The inflammation can affect all of the tissue layers in a given section, while leaving other sections healthy, according to the National Institute of Diabetes and Digestive and Kidney Disorders (NIDDK). Patients with Crohn's disease can have periods of active disease followed by periods of remission, says the Mayo Clinic. When the disease is active, patients suffer from varying degrees of abdominal cramping, diarrhea, ulcers of the intestines, and bloody stool. The intestines fail to efficiently absorb food, and this together with a loss of appetite can cause malnutrition and weight loss.
Old Theory
The Mayo Clinic says that doctors and scientists used to believe that a combination of dietary factors and stress caused Crohn's disease, but now this theory has been discounted. Factors like diet and stress are now viewed as agents that can increase the risk of developing the disease or worsening symptoms in patients already vulnerable to Crohn's disease. For example, the Mayo Clinic lists diets high in fat or refined foods as risk factors for the development of Crohn's disease.
New Theory
The NIDDK says that the most popular theory about the cause of Crohn's disease points to an immune system malfunction, in which the body mistakes normal intestinal bacteria and components of food as foreign invaders and launches an immune response that ultimately hurts the intestines themselves. Both the Mayo Clinic and NIDDK outline another theory which invokes a combination of the malfunctioning immune system and underlying genetic mutations.
Inflammation
People with Crohn's disease have an abnormally high level of an inflammatory protein called tumor necrosis factor or TNF in their intestines, but according to the NIDDK, it remains unclear if this and other alteration in the immune system are the cause of Crohn's disease, or its effects.
Genetics
The NIDDK says that African-Americans have a decreased risk for Crohn's disease, while people with Jewish ancestry have increased risk. These facts, together with the data showing that 20 percent of people with Crohn's disease have a close relative with inflammatory bowel disease, pointed scientists to the idea that a genetic mutation could cause some cases of Crohn's disease. According to the Mayo Clinic, people with Crohn's disease are more likely to have a mutation in the gene called NOD2 on the long arm of chromosome 16. Normally, the protein encoded by NOD2 helps cells engulf and presents foreign bacteria to the immune system, says Online Mendelian Inheritance in Man (CE-gene function section) and its mutation alters those processes.
