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Familial Adenomatous Polyposis (FAP) Syndrome

What is Familial Adenomatous Polyposis (FAP) Syndrome ?

Familial adenomatous polyposis (FAP) is a genetic disorder. It occurs when polyps (clumps of cells) form on the inside of a person’s colon (large intestine). These polyps can number in the hundreds to thousands. A milder form of FAP is called attenuated FAP (AFAP). Other polyposis syndromes are “variants” of FAP. They include Gardner and Turcot syndromes, as well as distinct disorders such as juvenile polyposis syndrome and Peutz-Jaegers syndrome.

Children with variant forms of FAP have polyps in the colon. They also have other symptoms that happen outside the colon. For example, someone with Gardner syndrome may have cysts and tumors in other parts of their body, such as under the skin or in the jaw.

If not treated, people with FAP will develop colon cancer in their lifetime. This often occurs before 40 years of age. Infants and young children with FAP are also at risk for a rare tumor of their liver called hepatoblastoma. They should be screened often for this cancer until they are 5-years old.

People with AFAP will have fewer polyps and lower cancer risk than with FAP. People with variant forms of FAP also are at increased risk for cancer. Rarely, colon cancers or other cancers can occur during childhood or the teen years.

What Causes FAP?

FAP is caused by a variant in a gene called APC. This gene tells the body how to make the APC protein. The APC protein helps cells work the right way. For example, this gene keeps cells from growing and splitting too fast or in a way that is not controlled. Variants in the APC gene can make the APC protein not able to control the cells that cause polyps that are not normal in the colon.

FAP is rare. Research suggests that less than one in 5,000 to 10,000 people have FAP. Variant forms of FAP are even rarer than FAP.

If one parent has FAP, a child has a one-half (50 percent) chance of having it, too. But, FAP is not always passed down (inherited). In fact, about one-fourth (25 percent) of patients with FAP are the first in their family to have it.

What are the Signs and Symptoms of FAP?

People with FAP are born with the condition. But they do not have gastrointestinal (GI) symptoms until the polyps grow greatly in size and number. This most often occurs between the ages of 8 and 20. Symptoms of FAP include:

  • Rectal bleeding
  • Belly pain
  • Low iron (Anemia)
  • Loose stools (Diarrhea)

The condition can be mild to severe, based on the variant in the APC gene. With FAP, the colon is the most common place for polyps to develop. But polyps also can develop throughout the GI tract.

How is FAP Diagnosed?

Doctors use two tests to diagnose FAP: a colonoscopy and genetic testing. The care team may advise one or both of these tests when symptoms of FAP appear. If the child has a family history of FAP, these tests may happen before symptoms appear. After a diagnosis of FAP, the doctor may order more tests to find out how severe the disease is.


A colonoscopy involves using a thin, flexible tube (colonoscope) to look inside the colon. At the tip of the tube is a tiny video camera. The doctor uses the camera to look at the inside of the colon. If the doctor sees polyps during the colonoscopy, he or she will remove a small amount of tissue. The tissue will be tested in the lab, to see if there are any signs of cancer. This tissue is removed through the colonoscope, not with an open surgery.

Finding one to three polyps during a colonoscopy is most often not a concern. But if the care team finds more than three polyps, more tests will be done. A person who has more polyps may be diagnosed with FAP or some other polyposis syndrome.

The polyps may become cancerous about 10 years after the polyps appear. Finding FAP early is vital. It can help the care team make a personalized treatment plan before symptoms start. If a child has a family history of FAP, the doctor may advise having a colonoscopy between the ages of 10 and 12, and then do a repeat colonoscopy every one to two years.

Genetic Testing

Genetic testing can confirm a diagnosis of FAP or variant forms of the disease. If a child has a family history of polyposis, the care team may advise that other family members have genetic testing for the disease as well.

Additional Testing

Other tests can be done to help the care team find out how severe the child’s condition is. This can also help find polyps in hard-to-reach parts of the GI tract. The tests include:

  • Video capsule endoscopy — This involves swallowing a pill-sized, wireless camera that takes video inside the GI tract.
  • Balloon-assisted enteroscopy — This helps check for and treat problems further into the small bowel. It can be used in place of surgery in some cases.
  • Endoscopic retrograde cholangiopancreatography (ERCP) — This procedure uses X-ray and an endoscope. An endoscope is a thin, flexible tube with a strong light and tiny camera. The test helps doctors see the small ducts that drain the pancreas, liver, and gall bladder into the small intestine. In young adults and some children, it is vital to look for polyps in these parts as well.

For infants and young children with FAP, abdominal ultrasound and blood tests are used to screen for hepatoblastoma. This is a rare liver tumor linked to FAP.

What Treatment is Available for Children with FAP?

A personalized care plan is vital, because the symptoms and concerns of each patient differ. This treatment plan should be based on a full evaluation from experts in pediatric gastroenterology, surgery, and human genetics.

Routine colonoscopies and other medical tests can provide helpful information to guide the decision making process. The care team may advise procedures to help delay surgery and reduce symptoms.

For patients with FAP, who are at a very high risk for colon cancer, this may include:

  • Taking out polyps found at screening colonoscopies to check for early signs of cancer.
  • Taking out polyps that are causing symptoms, either with endoscopic procedures or surgery.

Based on patient symptoms, genetic tests, and endoscopy results, you and your team may discuss surgery to remove the colon.

What Happens When Patients Must Have Their Colon Removed?

At some point, all people with FAP must have their colon removed. This lessens the risk of developing colon cancer. Surgery can happen during the teen years or early 20s, and even before if tests show signs of cancer. If there are no signs of cancer, timing for this surgery depends on many factors. Factors may include symptoms, family history, lab results and how many polyps are in the colon.

Surgery to remove the colon is called a colectomy. In most cases, the surgeon will also do a J-pouch surgery. This involves making a J-shaped reservoir out of a patient's small intestine to store and pass stool.

Doctors use the least invasive methods they can when operating on children with FAP. These can include laparoscopic and robotic procedures. This can lead to faster healing, less pain and a shorter hospital stay.

What is the Follow-Up Care After Surgery?

After surgery, the care team watches patients very closely for signs of infection or other problems. Most children who have had their colon removed will have bowel movements more often than other children. The care team will help them learn how to manage this so that they have the highest quality of life they can.

Children with FAP and variant forms of the disease need lifelong follow-up care to watch for signs of cancer and other concerns. Our expert team will guide their plan of care. Long-term follow-up may involve routine colonoscopies, ultrasound imaging and other tests.

What is the Long-Term Outlook for FAP Patients After the Colon is Removed?

Without surgery, the risk for colon cancer is nearly 100 percent. Taking out the colon greatly reduces a child’s risk for cancer,. but it does not fully remove the risk. This is because polyps may form in the very small portion of the colon left or in other parts of the GI tract. The rate of colon cancer among people with FAP, after colectomy, may be as high as four percent.

Long-term follow up care is vital for people with FAP and variant forms of the disease. They have a higher risk for cancer of the GI tract. They are also at increased risk for other cancers of the liver, adrenal gland, pancreas and thyroid.

Last Updated 12/2021

Reviewed By Emily Wakefield, LGC

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