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Familial Adenomatous Polyposis (FAP)
Monday, 26 January 2004
Sunday, 28 November 2004

What

Familial adenomatous polyposis (FAP) is a genetically inherited condition that causes a minimum of 100 (but up to thousands) of polyps (small projections of tissue) on the inside wall of the intestines, specifically the large intestine, or colon. The polyps typically occur in teenage years or early adulthood and have a very high risk of turning into colon cancer if preventive measures are not taken.

Who

FAP affects individuals who inherit changes in a gene called APC on chromosome 5. The disease occurs in the population in 1 out of every 10,000 persons, although some studies indicate the incidence may be as high as 1 in 31,000. There is no relationship between the disease and any particular gender or race.

Signs and Symptoms

Most individuals with FAP will start to have colonic polyps by adolescence (average age 16) or early adulthood. Individuals with polyps may show some or all of the following: • Unexplained rectal bleeding • Unexplained diarrhea • Unexplained abdominal pain • A mass in the abdomen or rectum that can actually be felt (more common in younger patients) • Abnormalities in teeth and skull (present in some variations of FAP) • Small cysts (bumps) on the skin (present in some variations of FAP) It is important to note that most people will have no symptoms whatsoever, regardless of the presence of the polyps. These individuals will later display symptoms as the polyps become cancerous.

Possible Causes

Most people with FAP have parents who are also affected with the disease. FAP is caused by inheriting one copy of a changed version of the APC gene. Every individual has two copies of every gene. People with FAP inherit one changed copy of the gene from their parents, and then the second copy becomes damaged during normal life. This results in the development of a polyp from the cells that have a damaged second copy. The reason the loss of the APC gene leads to cancer is that the APC gene makes a protein which monitors the activity of a protein called beta-catenin. Beta-catenin causes the increased activity of other genes, a hallmark of cancer. Thus the APC gene is referred to as a “tumor suppressor” gene. Without the product of the APC gene to monitor the activity of the beta-catenin, the increased activity can lead to cancer.

Diagnosis

FAP can be diagnosed by colonoscopy. A colonoscopy is an instrument with a small camera that is inserted into the anus and moved backward through the intestines to examine the lining of the colon and to look for polyps. A polyp can subsequently be removed by tools attached to the camera and the cells within it viewed under a microscope to determine the extent of the possible cancer-like changes within the cell. All adults in the population are recommended for regular screening for polyps starting at age 50, however individuals with a family history of FAP should have screenings at a much earlier age, as well as more frequently. If polyps in locations other than the colon are suspected, an esophagogastroduodenoscopy (a small camera is inserted through the mouth and moved forward through the GI tract) may be ordered by your doctor. These procedures are usually done with sedation. While these procedures may be slightly uncomfortable, there are preparations taken before the procedures to reduce the amount of discomfort. In a known family history of FAP, it may be advised to study a sample of your child’s DNA to look for specific changes in the APC gene. This type of test should also be accompanied by genetic counseling to help families interpret the results.

Treatment

Individuals with a family history of FAP will be checked regularly by colonoscopy (starting at age 12). Once the polyps have developed, a colectomy (removal of the colon) will be necessary as the probability of the polyps turning into cancer is almost 100%. This procedure is done in such a way as to not eliminate function of the rectum. With the onset of polyps and/or following surgery, a variety of drugs may be prescribed to assure that the polyps do not grow in other locations. Among the drugs that may be used are NSAIDs (non-steroidal anti-inflammatory drugs, similar to aspirin), which may reduce the size and number of polyps. Even following surgical removal of the colon, screening procedures will need to be regularly scheduled throughout the patient’s life.

Prognosis

If your teenager has FAP and is untreated, his/her life expectancy may be in the 30s to 50s, due to the high risk of colon cancer. People with FAP who receive treatment can be expected to have a much longer life expectancy. .

Connect with other parents

In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.

Weblinks

FAP Support Group
This is a website to a support group specifically for families with FAP.

Julie's Story
A great website with a personal story as well as detailed information about the disease and various treatment options.

Google Search for Familial Adenomatous Polyposis (FAP)

References and Sources

Nussbaum RL., McInnes RR, Willard HF (2001). Thompson and Thompson Genetics in Medicine 6th ed. Philadelphia, PA: W.B. Saunders, p. 326-327 Kumar V, Cotran RS, Robbins SL (2003). Robbins Basic Pathology 7th ed. Philadelphia, PA: Saunders, p. 581-583 Carethers, JM. “Familial Adenomatous Polyposis” http://www.emedicine.com/med/topic769.htm