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What is Crohn’s disease?
Crohn’s disease (CD) is a chronic disease that can cause inflammation anywhere along the digestive tract from the mouth to the anus. Of all cases of CD, 45% occur in ileum and colon, 35% in just the ileum, and 20% in just the colon. Unlike ulcerative colitis (UC), which only affects the inner layer, CD commonly involves all layers of the intestinal wall. CD and UC are collectively called inflammatory bowel disease.
What are the symptoms of CD?
Common symptoms of CD include chronic diarrhea fever, abdominal pain, weight loss, and lack of appetite. Frequent diarrhea can lead to dehydration and nutritional deficiencies.
Because the colon is inflamed, it is not as efficient at absorbing water and nutrients from food. Fever is a characteristic of the inflammatory process, may be either high or low-grade, and presents especially during periods of active disease. Night sweats are caused by a fever spiking repeatedly during the night.
Extra-intestinal symptoms include eye inflammation, joint pains, skin rashes or lesions, fistulas and fissures. It is unclear why symptoms develop outside the digestive tract, but they often decrease in severity along with flare-ups.
Eye conditions that can occur with CD include conjunctivitis, episcleritis, uveitis, iritis and keratopathy. Most eye conditions will improve when progress is made in treating the underlying CD, but some may require treatment. Conjunctivitis, or “pink eye,” is an inflammation of the tissue covering the eye and inner surface of the eyelid and may be treated with antibiotics. Uveitis is the inflammation of the middle layer of the eye wall and symptoms include light sensitivity, pain, redness, blurred vision and headaches. Uveitis is commonly treated with corticosteroids; if left untreated it could result in glaucoma or detached retina. Inflammation in the white of the eye is called episcleritis: symptoms include pain and reddening, and treatment is with a vasoconstrictor or corticosteroid. Iritis is inflammation in the iris and symptoms include pain, light sensitivity, blurred vision, redness, decreased pupil size, and floaters. Steroids and antibiotics may be used to treat iritis. Keratophaty is an irregularity in the cornea that does not cause pain or loss of vision, and is therefore usually not treated.
Joint pains may be peripheral arthritis, which causes pain, swelling, and stiffness in the joints. The pain can migrate from one joint to the next and may last for several days or even weeks. Peripheral arthritis does not cause permanent damage to joints and will often improve when the CD is successfully treated. Treatment includes resting painful joints and applying moist heat. Other forms of arthritis may also occur with CD.
Erythema nodosum and pyoderma gangrenosum are skin conditions that may occur before or during a CD flare-up and improve with remission. Erythema nodosum are painful red nodules that develop on the arms or lower legs that affects more women than men. Pyoderma gangrenosum may appear as a blister on the legs or arms, usually at the site of a minor trauma such as a cut. The blister may progress into an ulcer that requires treatment with steroids or antibiotics.
A fissure is a tear or ulcer in the lining of the anal canal and symptoms include painful bowel movements, bright red blood in toilet bowel or on paper, anal lump, and swollen skin tag. Acute fissures may be treated with Sitz baths, fiber to create softer stools, stool softeners, topical hydrocortisone, zinc oxide, petroleum jelly and topical anesthetics. A chronic fissure may need more aggressive treatment including surgery.
A fistula is an abnormal tunnel connecting two body cavities or a body cavity to the skin. Approximately 30% of people with Crohn's Disease develop fistulas. Treatments include antibiotics, immunosuppresants, Remicade, liquid nutrition to replace solid food and surgery.
Are there different forms of CD?
Physicians may use different terms to describe CD, depending on what part of the digestive tract is affected.
The most common form of CD is ileocolits, which affects the ileum (lower end of the small intestine) and the colon (large intestine). Symptoms of this type of CD include diarrhea, cramping pain in the lower right or middle abdomen, and substantial weight loss. In some cases the diseased areas in the ileum and the colon may be contiguous, affecting the ileocecal valve that connects the two sections.
Ileitis, also known as fistulizing or perforating CD, affects only the ileum. Diarrhea, cramping pain in the the lower right or middle abdomen, and discomfort a few hours after eating a meal are common symptoms.
This type of CD can lead to nutritional deficiencies in B12, causing tingling in the fingers or toes (peripheral neuropathy), or folate, which may result in anemia. Complications can include fistulas or abscesses in the right lower quadrant.
Gastroduodenal CD affects the stomach and duodenum (first part of the small intestine). Symptoms include loss of appetite, weight loss, nausea, and vomiting. Vomiting may be a sign of obstruction in narrowed portions of the small intestine. This form of CD is sometimes misdiagnosed as an ulcer, with the CD being discovered after ulcer treatments are ineffective in relieving symptoms.
Jejunoileitis is characterized by intermittent areas of inflammation in the jejunum (middle section of the small intestine). Symptoms include crampy pain after meals, diarrhea, and abdominal pain that can vary from mild to intense. Complications of jejunoileitis include fistulas and malnutrition caused by poor absorption of nutrients.
Crohn's colitis (CC), sometimes called granulomatous colitis, affects only the colon and is sometimes confused with UC. However, there are two distinct differences between CC and UC: inflammation in UC is always contiguous, while in CC it is intermittent throughout the colon, and UC always affects the rectum while CC may not. Symptoms include diarrhea, bleeding from the rectum, and abscesses, fistulas, or ulcers around the anus. Peripheral arthritis and skin conditions are found more frequently with CC than the other types of CD.
What causes CD?
Scientists are not certain what causes CD, so it is known as an idiopathic disease, or a disease with unknown cause. However, there are theories about the origins of CD.
CD is an autoimmune disease, or a disease that is triggered by the immune system. The medical community has noticed seasonal flare-ups (in the spring or autumn) in people with IBD. One theory is that this is a IgE-mediated allergic response.
IgE is a type of immunoglobulin isotype, which is a special protein that helps inactivate organisms that may cause disease. The function of IgE is to bind itself to an antigen and inactivate or remove offending foreign substance. However, IgE tends to attach itself to receptors on mast cells which triggers allergy symptoms such as a runny nose. If an antigen binds itself to one of these IgE cells, the mast cells are activated, and release histamine, heparin, cytokines, leukotrines, and other chemicals.
The presense of leukotrines attracts a new type of cell called an eosinophil. These cells fight off the allergic response, but the chemicals that they use to do so are toxic to the body as well as to the invading infection. The connection between eosinophils and IBD is that three of the four toxic compounds that are released by eosinophil cells are found in in the stool of IBD patients.
A controversial theory is that the bacteria M. paratuberculosis can also cause CD in humans. One study conducted on intestinal tissue removed during surgery from patients with CD, UC or without IBD found that 65% of the CD patient samples contained the bacteria, contrasting with only 12.5% of non-IBD patients. The researchers conclude that the bacteria may play a role in some cases of Crohn's disease.
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