context: Crohn's disease, also known as ileitis or regional enteritis, is a chronic illness. In Crohn's, the intestine, bowel, or other part of the digestive tract becomes inflamed and ulcerated -- marked with sores. Along with ulcerative colitis, Crohn's disease is part of a group of diseases known as inflammatory bowel disease ( IBD). Crohn's disease usually affects the lower part of the small intestine, which is called the ileum, and the beginning of the colon. The disease, though, can occur in any part of the gastrointestinal system. Thus, the disorder may affect the large or small intestine, the stomach, the esophagus, or even the mouth. Crohn's can occur at any age. It is most commonly diagnosed in people who are between the ages of 15 and 30. The symptoms of Crohn's disease depend on where in the bowel the disease occurs. They also depend on its severity. Symptoms can include: abdominal pain and tenderness (often on the lower right side of the abdomen) chronic diarrhea delayed development and stunted growth (in children) feeling of a mass or fullness in the lower right abdomen fever rectal bleeding weight loss Other symptoms can develop, depending on complications related to the disease. For example, a person with a fistula, an abnormal passageway, in the rectal area may have pain and discharge around the rectum. Other complications from Crohn's disease include: arthritis gallstones inflammation of the eyes and mouth kidney stones liver disease skin rashes or ulcers The cause of Crohn's disease is not known. It is likely that there is a genetic component. About 20% of people with Crohn's disease have a blood relative with a form of IBD. People of Jewish heritage have a greater risk of developing Crohn's. Crohn's disease may involve the immune system. The immune system of a person with Crohn's may treat bacteria, food, and other substances as foreign invaders, leading to chronic inflammation from the accumulation of white blood cells in the lining of the intestines and resulting in ulcerations and injury to the tissues. A number of tests are used to distinguish Crohn's disease from other gastrointestinal conditions. First, your doctor will review your medical history. This information is helpful because Crohn's disease is more common in people who have a first-degree relative -- mother, father, sister, or brother -- with IBD. After a physical examination is done, the doctor may order the following tests: Endoscopy (such as colonoscopy or sigmoidoscopy): During this procedure, a flexible, lighted tube called an endoscope is inserted into the rectum and used to view the inside of the rectum and colon. A colonoscopy shows a greater portion of the colon than a sigmoidoscopy does. A small sample of tissue may be taken for testing -- biopsy. An upper endoscopy may also be used to look down the esophagus, into the stomach and the first part of the small intestine, the duodenum. A capsule endoscopy uses a pill with a camera inside that is swallowed and takes pictures of the small intestine Blood tests: When testing the blood, the doctor will look for signs of anemia or a high white blood cell count that could indicate inflammation or infection somewhere in the body. Barium X-ray (barium enema or small bowel series): X-rays are often taken of either the upper or lower intestine. Barium coats the lining of the small intestine and colon and shows up white on an X-ray. This characteristic enables doctors to view any abnormalities. CT scans and an MRItaken with oral contrast are other imaging tests that are used. There is no cure for Crohn's disease. The goals for treatment are: to reduce inflammation to relieve symptoms of pain, diarrhea, and bleeding to eliminate nutritional deficiencies Treatment might involve drugs, nutritional supplements, surgery, or a combination of these therapies. Treatment choices depend upon where the disease is located and how severe it is. They also depend on the complications associated with the disease and the way the person has responded in the past to treatment when symptoms recurred. There are several types of drugs used to treat Crohn's disease. The first step usually involves reducing inflammation. Many people are first treated with sulfasalazine ( Azulfidine). Mesalamine ( Asacol, Canasa, Pentasa) is another 5-aminosalicylic acid, or 5- ASA medication. Possible side effects of sulfasalazine and other mesalamine-containing drugs may include: nausea vomiting diarrhea heartburn headache If a person does not respond to sulfasalazine, the doctor may prescribe other types of drugs that contain 5- ASA. These other products include: olsalazine ( Dipentum) balsalazide ( Colazal, Giazol) mesalamine ( Asacol, Lialda, Pentasa, and others) Corticosteroids such as prednisone are another class of drugs that reduce inflammation. A doctor is likely to prescribe an initial large dose of prednisone when the disease is very active. The dose is then tapered off. A problem with corticosteroids is the large number of possible side effects -- some of them serious -- such as a higher susceptibility to infection and stomach ulcers. Crohn's disease may also be treated with drugs that stop the immune system from causing inflammation. Immunomodulators change the way the immune system behaves. Immunosuppressants decrease the activity of the immune system. Immunostimulators increase the activity. Immunosuppressants prescribed for Crohn's disease include: azathioprine ( Azasan, Imuran) cyclosporine 6-mercaptopurine (6 MP, Purinethol) tacrolimus ( Prograf) Methotrexate ( MTX, Rheumatrex, Trexall) Side effects of immunosuppressants may include: diarrhea higher susceptibility to infection nausea vomiting Biologic drugs such as infliximab ( Remicade) or infliximab-dyyb ( Inflectra), a biosimilar to Remicade, are often prescribed when a person with Crohn's disease does not respond to the standard treatments of 5 ASA-containing drugs, corticosteroids, and immunosuppressants. Infliximab is an antibody that attaches itself to the inflammation-promoting protein, tumor-necrosis factor-alpha ( TNF-alpha). Other anti- TNF medications are adalimumab ( Humira) and adalimumab-atto ( Amjevita), a biosimilar to Humira. These drugs are also used to treat other immune system disorders such as rheumatoid arthritis. Certolizumab ( Cimzia) is another anti- TNF blocker approved for Crohn's disease. There are other biologic alternatives to the anti- TNF blockers. Two drugs block alpha-4 integrin -- natalizumab ( Tysabri) and vedolizumab ( Entyvio). Ustekinumab ( Stelara) works in another way by targeting other proteins, IL-12 and IL-23. Other substances that may be prescribed to treat Crohn's include: Antibiotics to treat bacterial infections and overgrowth of bacteria in the small intestine; types of antibiotics commonly prescribed include: ampicillin ( Omnipen)cephalosporinsfluoroquinolones ( Ciprofloxacin)metronidazole ( Flagyl)sulfonamidestetracycline Antidiarrheal agents to stop diarrhea Fluid replacements to counteract dehydration Nutritional supplements to provide the nutrients that may not be absorbing properly