Familial adenomatous polyposis (patient information)

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Familial Adenomatous Polyposis


What are the symptoms?

What are the causes?

Who is at highest risk?


When to seek urgent medical care?

Treatment options

Where to find medical care for familial adenomatous polyposis?


What to expect (Outlook/Prognosis)?

Possible complications

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Sadaf Sharfaei M.D.[2]


Familial adenomatous polyposis (FAP) is an inherited disorder characterized by cancer of the large intestine (colon) and rectum. People with the classic type of familial adenomatous polyposis may begin to develop multiple noncancerous (benign) growths (polyps) in the colon as early as their teenage years. Unless the colon is removed, these polyps will become malignant (cancerous). The average age at which an individual develops colon cancer in classic familial adenomatous polyposis is 39 years. Some people have a variant of the disorder, called attenuated familial adenomatous polyposis, in which polyp growth is delayed. The average age of colorectal cancer onset for attenuated familial adenomatous polyposis is 55 years.

In people with classic familial adenomatous polyposis, the number of polyps increases with age, and hundreds to thousands of polyps can develop in the colon. Also of particular significance are noncancerous growths called desmoid tumors. These fibrous tumors usually occur in the tissue covering the intestines and may be provoked by surgery to remove the colon. Desmoid tumors tend to recur after they are surgically removed. In both classic familial adenomatous polyposis and its attenuated variant, benign and malignant tumors are sometimes found in other places in the body, including the duodenum (a section of the small intestine), stomach, bones, skin, and other tissues.

What are the Symptoms of familial adenomatous polyposis?

Most familial adenomatous polyposis do not cause symptoms. If you have symptoms, they may include blood on your underwear or on toilet paper after a bowel movement, blood in your stool, or constipation or diarrhea lasting more than a week. Patients might have

What Causes familial adenomatous polyposis?

Mutations in the APC gene and MUTYH gene cause both classic and attenuated familial adenomatous polyposis. These mutations affect the ability of the cell to maintain normal growth and function. Cell overgrowth resulting from mutations leads to the colon polyps seen in familial adenomatous polyposis.

Who is at Highest Risk?

Patients with positive family history of colorectal polyps are at highest risk of familial adenomatous polyposis.


Familial adenomatous polyposis is diagnosed based on clinical presentation, genetic testing, and imagings.

Treatment Options

The best treatment option is to remove large bowel.

Where to find Medical Care for familial adenomatous polyposis?

Medical care for familial adenomatous polyposis can be found here.


Genetic counseling is used for high risk individuals to prevent familial adenomatous polyposis in families.

What to Expect (Outlook/Prognosis)?

All the patients with familial adenomatous polyposis would develop colon cancer, if left untreated. However, prognosis is excellent if large bowel is removed.

Possible Complications

All the patients with familial adenomatous polyposis would develop colon cancer, if left untreated.