Familial Adenomatous Polyposis

Familial Adenomatous Polyposis (FAP) is a rare, inherited condition causing hundreds to thousands of noncancerous growths called polyps in the large intestine (colon) and rectum. These polyps almost always become cancerous if not removed, typically by age 40. Early diagnosis and surgical treatment are crucial to prevent colon cancer.

What is Familial Adenomatous Polyposis?

Familial Adenomatous Polyposis (FAP) is a rare genetic disorder that causes numerous noncancerous growths, called polyps, to develop mainly in the large intestine (colon) and rectum. These polyps usually begin forming in the teenage years and have a nearly 100% chance of turning into colon cancer if left untreated, often by age 40.

FAP is an inherited condition, meaning it is passed down through families. It affects about 1 in 10,000 people. The defining feature of FAP is the development of hundreds to thousands of polyps throughout the colon and rectum. While these polyps are not cancerous at first, they almost certainly will become cancerous over time. There are different forms of FAP. Classic FAP involves the growth of hundreds or even thousands of polyps. Another form, called attenuated FAP (AFAP), causes fewer polyps (usually less than 100) and these polyps tend to appear later in life, often in adulthood. Both forms carry a very high risk of colon cancer. Beyond the colon, FAP can also cause other growths in different parts of the body. These can include polyps in the stomach and small intestine, as well as noncancerous tumors such as osteomas (benign bone growths, often in the jaw), dental abnormalities, and desmoid tumors (noncancerous but aggressive growths in connective tissue). Some people with FAP may also have a higher risk of developing certain other cancers, such as thyroid cancer.

Symptoms

In its early stages, Familial Adenomatous Polyposis (FAP) often causes no noticeable symptoms, even as polyps begin to form. As the polyps grow larger or become more numerous, common symptoms can include blood in the stool, changes in bowel habits like diarrhea or constipation, abdominal pain, and unexplained weight loss.

Many people with FAP do not experience any symptoms until the polyps become large or very numerous, or until cancer has developed. This is why regular screening is so important for individuals at risk. When symptoms do appear, they can include rectal bleeding, which might be visible in the stool or on toilet paper. You might also notice changes in your usual bowel habits, such as persistent diarrhea or constipation. Some people experience abdominal pain or cramping. Other general symptoms that can occur with FAP include unexplained weight loss and feeling very tired (fatigue). These symptoms are not unique to FAP and can be caused by many different conditions, so it's important to see a doctor for a proper diagnosis.

Causes & risk factors

Familial Adenomatous Polyposis (FAP) is caused by a specific change (mutation) in a gene called APC. This mutation is usually inherited from a parent, making a family history of FAP the primary risk factor. In some cases, the mutation can occur spontaneously, meaning it's not inherited.

The main cause of FAP is a mutation in the adenomatous polyposis coli (APC) gene. This gene normally acts as a tumor suppressor, helping to control cell growth. When the APC gene is mutated, it can't do its job properly, leading to uncontrolled cell growth and the formation of polyps. FAP is an autosomal dominant condition. This means that if you inherit just one copy of the altered APC gene from either parent, you will develop the condition. If a parent has FAP, each of their children has a 50% chance of inheriting the mutated gene and developing FAP. While most cases of FAP are inherited, about 15% to 20% of people with FAP develop the condition due to a new, spontaneous mutation in the APC gene. This means they are the first in their family to have the condition, and neither parent carries the mutation.

How it's diagnosed

Familial Adenomatous Polyposis (FAP) is typically diagnosed through a combination of reviewing your family medical history, performing a colonoscopy to visually inspect the colon for polyps, and conducting genetic testing. Genetic testing specifically looks for the APC gene mutation, confirming the diagnosis and identifying at-risk family members.

The diagnostic process usually begins with a thorough review of your personal and family medical history. If there's a known history of FAP or early-onset colon cancer in your family, your doctor will likely recommend further testing. A key diagnostic tool is a colonoscopy. During this procedure, a doctor uses a flexible tube with a camera to examine the inside of your entire colon and rectum. This allows them to identify and count polyps, and to take tissue samples (biopsies) for examination under a microscope. For individuals at risk, colonoscopies usually begin at a young age, often between 10 and 12 years old, and are repeated regularly. Genetic testing is crucial for confirming a diagnosis of FAP. A blood test can identify the specific mutation in the APC gene. This test is important not only for diagnosing the affected individual but also for identifying other family members who may be at risk and need screening.

Treatment options

The primary treatment for Familial Adenomatous Polyposis (FAP) is surgery to remove the colon and rectum, which is almost always necessary to prevent colon cancer. After surgery, ongoing surveillance is essential to monitor for any new polyps or other related growths. Certain medications may also be used as additional therapy but do not replace surgery.

Surgery is the cornerstone of FAP treatment and is almost always recommended to prevent colon cancer. This typically involves removing most or all of the large intestine (colectomy). There are several surgical options, depending on the number and location of polyps and the patient's overall health. These can include removing the entire colon and rectum (proctocolectomy) or removing most of the colon while leaving the rectum (total colectomy with ileorectal anastomosis). After surgery, regular follow-up care is vital. This includes ongoing endoscopic surveillance of any remaining bowel tissue to check for new polyps. Doctors will also recommend screening for other potential growths or cancers associated with FAP, such as those in the upper digestive tract (stomach and small intestine) and the thyroid gland. Some medications, such as certain nonsteroidal anti-inflammatory drugs (NSAIDs) like celecoxib, may be used as an additional (adjunctive) treatment. These medications might help reduce the number or size of polyps in the colon and rectum. However, they do not eliminate the risk of cancer and are not a substitute for surgical removal of the colon. The effect of celecoxib on preventing cancer or avoiding surgery is unclear.

Recovery & outlook

The outlook for individuals with Familial Adenomatous Polyposis (FAP) is significantly improved with early diagnosis and timely surgical treatment, which dramatically reduces the risk of colon cancer. Without treatment, colon cancer is almost certain by age 40. Recovery after surgery involves careful monitoring and lifelong surveillance for other potential FAP-related conditions.

If FAP is left untreated, nearly all individuals (almost 100%) will develop colon cancer, often by the age of 40. However, with early diagnosis and appropriate surgical intervention, the risk of colon cancer is greatly reduced, and the outlook is much more positive. Recovery from surgery for FAP involves a period of healing and adjustment. Depending on the type of surgery, you may need to adapt to changes in bowel function. Lifelong medical surveillance is crucial after surgery. This includes regular check-ups and endoscopic procedures to monitor for any new polyps in remaining bowel segments or in the upper digestive tract (stomach and duodenum). Individuals with FAP also need to be monitored for other potential complications, such as desmoid tumors (noncancerous but aggressive growths) and an increased risk of other cancers, including thyroid cancer. Adhering to a comprehensive surveillance plan developed with your medical team is essential for managing FAP long-term and maintaining good health.

When to see a doctor

You should see a doctor if you experience symptoms like blood in your stool, persistent changes in bowel habits (diarrhea or constipation), unexplained abdominal pain, or weight loss. If you have a family history of Familial Adenomatous Polyposis (FAP) or early-onset colon cancer, it is crucial to discuss screening with your doctor, even if you have no symptoms.

It is important to consult a doctor if you notice any new or concerning digestive symptoms. These include seeing blood in your stool, experiencing ongoing diarrhea or constipation, or having abdominal pain that doesn't go away. Unexplained weight loss or persistent fatigue should also prompt a medical evaluation. If you have a close relative (parent, sibling, or child) diagnosed with FAP, or if there's a strong family history of colon cancer diagnosed at a young age, you should speak with your doctor immediately. Even without symptoms, genetic counseling and testing may be recommended to determine your risk. For individuals diagnosed with FAP or those at high risk, regular screening colonoscopies typically begin in early adolescence, often between ages 10 and 12. Following your doctor's recommended surveillance schedule is vital for early detection and prevention of cancer.

Frequently asked questions

Is FAP always inherited?

Familial Adenomatous Polyposis (FAP) is usually inherited from a parent, meaning it runs in families. However, in about 15% to 20% of cases, the genetic mutation that causes FAP can occur spontaneously, meaning the person is the first in their family to have the condition.

Can FAP be cured without surgery?

No, surgery is almost always necessary to prevent colon cancer in individuals with FAP. While some medications, like certain NSAIDs, can help reduce the number of polyps, they do not eliminate the risk of cancer and are not a substitute for surgical removal of the colon.

What is the risk of colon cancer with FAP?

Without treatment, individuals with Familial Adenomatous Polyposis (FAP) have a nearly 100% chance of developing colon cancer, often by age 40. Early diagnosis and surgical removal of the colon dramatically reduce this risk.

What other health problems can FAP cause besides colon polyps?

FAP can cause polyps in other parts of the digestive tract, such as the stomach and small intestine. It can also lead to noncancerous growths like desmoid tumors (growths in connective tissue), osteomas (bone growths), and dental abnormalities. There's also an increased risk of certain other cancers, including thyroid cancer.

How often do people with FAP need to be screened?

Individuals at risk for FAP typically begin screening colonoscopies between ages 10 and 12, with repeat screenings every 1-2 years. After surgery, lifelong surveillance is needed, including regular endoscopies of any remaining bowel and monitoring for other FAP-related conditions, as advised by their doctor.

What is the difference between classic FAP and attenuated FAP?

Classic FAP causes hundreds to thousands of polyps in the colon and rectum, usually appearing in the teenage years. Attenuated FAP (AFAP) causes fewer polyps (typically less than 100) and these polyps tend to develop later in life, often in adulthood. Both forms carry a high risk of colon cancer.

Sources

• MedlinePlus — Familial Adenomatous Polyposis
• Mayo Clinic — Familial Adenomatous Polyposis
• Cochrane Library — Familial Adenomatous Polyposis