Gastrointestinal polyposis is the presence of many growths (polyps) in the gastrointestinal tract. The rare familial adenomatous polyposis (FAP) is the most common of these syndromes. Hundreds to thousands of noncancerous (benign) polyps grow in the large intestine (colon or bowel) and rectum. Some people have a different type of the disorder called attenuated FAP, which is accompanied by delayed polyp growth.
People of all races can get it—males and females equally.
FAP is an inherited autosomal dominant disorder. Autosomal dominant means that having only one parent with the abnormal gene can give a child a 50% chance of having the disorder. A germline mutation of the APC tumor suppressor gene is the cause. A germline mutation is found in all body cells. The APC gene controls cell growth and cell death. People with a mutated (changed) gene have a higher risk of having polyps and cancer.
People often have a family history of the syndrome or of colorectal cancer. Nonspecific symptoms, such as rectal bleeding, diarrhea, abdominal pain, or desmoid tumors, may suggest FAP in young people. Polyps usually start to grow at age 16. Most people don’t have symptoms until they get colon cancer at an early age (usually before age 50).
Cancer screening often begins in childhood. Colonoscopy is essential to rule out malignant changes in polyps. The health care provider also uses genetic testing, upper endoscopy, and may also order computed tomography (CT scan).
A medical history (especially family history) and physical examination are also important for diagnosis. An eye examination with a slit lamp can find many flat pigmented lesions in the retinas. Masses that the health care provider can feel in the abdomen (belly) and rectum in young people suggest FAP.
Hundreds to thousands of polyps form, so they cannot be removed separately. Surgery to remove the whole colon (colectomy) is the only effective treatment. It greatly improves life expectancy. Surgery can be done in adulthood. However, because of the high colon cancer risk, sometimes early ileal-pouch anal anastomosis (IPAA) is done instead of colostomy. Most people can eat normal diets and lead normal lives after surgery. Surgery doesn’t cure the disease, however, and polyps continue to form. Certain medicines (sulindac, celecoxib) may make polyps shrink or prevent new growths. These drugs should be used only with regular check-ups and screening. Upper endoscopy to find polyps, genetic testing, and screening of family members are needed.
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