Autoimmune diseases occur due to a malfunction of the immune system, causing it to attack healthy cells and tissues in the body. The American Autoimmune Related Diseases Association reports that 23.5 million Americans suffer from an autoimmune disease, which is higher than the 22 million who suffer from heart disease. With between 80 to 100 diseases known to exhibit autoimmune characteristics and because many autoimmune diseases affect many organs at once, autoimmune diseases exhibit a variety of symptoms. Many autoimmune diseases, even those that do not directly affect the stomach, cause abdominal pain.
Pernicious anemia describes a specific type of anemia--a low level of red blood cells--caused by an autoimmune disease in which the immune system attacks the parietal cells of the stomach. The parietal cells function to produce a protein known as intrinsic factor, which is necessary for the body to absorb vitamin B12. Without intrinsic factor, a vitamin B12 deficiency occurs, and without vitamin B12 the body cannot produce new red blood cells. This autoimmune disease therefore results in pernicious anemia, which causes symptoms including fatigue, shortness of breath, dizziness, headache, numbness and tingling in the hands and feet and pale skin.
The destruction of the parietal cells resulting in pernicious anemia produces symptoms in the digestive tract, according to the National Heart, Lung and Blood Institute. These symptoms include nausea, vomiting and abdominal pain due to heartburn, gas, bloating, constipation and diarrhea.
Crohn's disease, classified as an autoimmune disease, occurs due to the immune system mistakenly attacking bacteria, foods and other substances in the digestive tract. Accumulation of white blood cells in the lining of the intestines can result chronic inflammation and bowel injury, as described by the National Digestive Diseases Information Clearinghouse.
Classified as an irritable bowel disease, Crohn's disease damages all layers of the intestines while allowing some sections to remain healthy. This characteristic helps to differentiate Crohn's disease from similar diseases, such as ulcerative colitis. Crohn's disease causes chronic abdominal pain and diarrhea often accompanied by rectal bleeding, weight loss, arthritis, skin problems and fever.
Ulcerative colitis, similar to Crohn's disease, is classified as an autoimmune disease and belongs to the group of irritable bowel diseases. Ulcerative colitis causes inflammation and the formation of tiny sores, known as ulcers, on the lining of the colon and rectum. The most common symptoms include abdominal pain and bloody diarrhea, which contribute to the other symptoms of fatigue, weight loss, loss of appetite and growth failure.