Familial Adenomatous Polyposis (FAP)

Familial Adenomatous Polyposis (FAP)

Although familial adenomatous polyposis (FAP) is a serious condition that may become life-threatening, it can be detected early and treated successfully. With prompt treatment, FAP patients lead normal, healthy lives. Untreated, FAP will lead to colon cancer.

Because this condition is always hereditary, family members of those with the condition also are at risk of developing it. FAP can be diagnosed by a blood test to detect a genetic mutation in the APC gene, which causes FAP, or by flexible sigmoidoscopy, a simple, painless examination of the lower colon that is performed at a doctor’s office. We strongly encourage those at risk to consider genetic testing or flexible sigmoidoscopy done either by your family physician or by one of our specialists.

Below are answers to questions we are most often asked by people at risk of developing FAP.

What is FAP?

FAP is an inherited condition, where polyps develop in the intestinal tract, but primarily it affects the large intestine, including the colon and rectum. It is due to a genetic mutation that interferes with the normal function of APC, an important gene that controls how quickly cells grow. The gene mutation is most often inherited from a parent, but 30 percent of FAP patients develop the mutation during conception and do not have a parent with FAP.

Those who inherit the gene mutation develop numerous adenomatous polyps, which are precancerous growths, in the lining of the colon and rectum. If undetected and untreated, one or more of the polyps will eventually become cancerous. Fortunately, with early diagnosis and treatment, FAP patients can avoid cancer and lead normal, healthy lives.

How is FAP inherited?

Each child of a parent with FAP has a 50 percent chance of inheriting the gene. Those who have inherited the gene for FAP will eventually develop polyps and may pass along the condition to their children. However, those who have not inherited the gene have only the “normal” risk of developing large bowel polyps and cannot pass FAP to their children.

Are other relatives at risk?

In families, everyone who has a parent with FAP is at risk for developing the condition. Other family members may not be aware of their own risk, or they may mistakenly think the absence of symptoms means an absence of risk. Unfortunately, this lack of awareness can lead to the development of colon cancer. That is why we feel a great responsibility to contact and inform family members of their risk. Once informed, we encourage everyone to take the steps that will prevent colon cancer.

Do colon polyps in FAP always become cancerous?

If untreated, yes. Colon polyps can become cancerous in the teenage years, but this happens more commonly in the 20s and 30s. By age 40, almost all untreated patients will have developed colon cancer. Fortunately, early treatment prevents colon cancer from ever developing.

Does FAP have symptoms?

In its early stages, FAP has no symptoms. That is why genetic testing or endoscopic screening starting at puberty when polyps first appear is so important. The diagnosis can and should be made before symptoms and colorectal cancer occur.

If untreated, polyps will increase in number and size. Patients may have hundreds of polyps in their colon without symptoms. As the condition progresses, patients may experience blood in the stool, diarrhea, mucous discharge, crampy abdominal pain, anemia, weight loss and intestinal obstruction. However, these symptoms may not occur until the condition has become cancerous.

How is FAP detected?

There is a genetic blood test for FAP that will detect most mutations in the APC gene. Prior to arranging genetic testing, a counseling session is arranged with physicians and genetic counselors in the Jagelman Registries. At this session, people learn more about FAP, the implications of genetic testing and the course of action that should be taken. Once the mutation is found in a family member, it is easy and cheap to check for the mutation with other relatives who are at risk.

If the mutation is not found in other family members, they do not have FAP and don’t need further testing. Those with the mutation need to have a procedure called a colonoscopy which enables the physician to examine the entire colon and rectum with a small lighted tube. If no polyps are found, we recommend this examination once a year. It is recommended that this examination be performed starting at age 10-12. Most patients with FAP develop polyps by age 20.

How is FAP treated?

When polyps are found, the only effective treatment is surgical removal of the large bowel because the polyps are too numerous and fast-growing to be removed individually by colonoscopy. While the prospect of surgery may be upsetting, it is important to realize that without it, colon cancer is inevitable.

With surgery, colon cancer can be prevented. There are two main types of operations used in treating FAP, and your physician will recommend which one is best for you. These operations can often be done laparoscopically, making the procedure less painful and less debilitating.

Can FAP affect other organs?

Although FAP always affects the colon, the mutation is present in every cell in the body and other organs are affected. Almost everyone with FAP develops polyps in the stomach and duodenum. These need to be checked by EGD starting at age 20 and continuing every few years. The gastric polyps are usually not precancerous, but the duodenal polyps, called adenomas, are precancerous. Cancer can occur in the duodenum, but in most FAP patients it is rare. Desmoid tumors are overgrowths of scar tissue that develop in about 12 percent of FAP patients. They need specialized care. Other organs that can be affected include the brain, thyroid, bones, skin and teeth.


If you would like more information about FAP, please contact us at:

The David G. Jagelman Inherited Colorectal Cancer Registries

Department of Colorectal Surgery/A30

Cleveland Clinic

9500 Euclid Ave.

Cleveland, OH 44195

Phone: 216.444.6470 or 800.223.2273 ext. 46470

Cleveland Clinic and Cleveland Clinic Florida welcome anyone who wishes to be treated by our Registries team. You may make an appointment yourself, or your physician may refer you to one of our specialists. Please call Cleveland Clinic at 216.444.5404 or 800.223.2273 ext. 45404.