Familial Adenomatous Polyposis (FAP) is a rare inherited disorder that significantly increases the risk of colorectal cancer. Although uncommon, it is one of the most important hereditary cancer syndromes because, without timely diagnosis and treatment, nearly every affected individual will eventually develop colorectal cancer.
The encouraging news is that advances in genetic testing, colonoscopy, preventive surgery, and lifelong surveillance have dramatically improved outcomes. When diagnosed early, people with FAP can receive timely treatment that greatly reduces their cancer risk and allows them to lead long, productive lives.
In this guide, we’ll explain everything you need to know about Familial Adenomatous Polyposis in simple language—from symptoms and diagnosis to treatment options, surgery, and frequently asked questions.
What Is Familial Adenomatous Polyposis?
Familial Adenomatous Polyposis (FAP) is an inherited genetic condition that causes hundreds to thousands of adenomatous polyps to develop in the colon and rectum.
Adenomatous polyps are non-cancerous growths, but they have the potential to become cancerous over time. In people with FAP, these polyps usually begin appearing during adolescence or early adulthood.
Without treatment, the lifetime risk of colorectal cancer approaches 100%, usually before the age of 40.
FAP is caused by mutations in the APC (Adenomatous Polyposis Coli) gene, a tumour suppressor gene responsible for regulating cell growth. When this gene is altered, abnormal cell growth occurs, leading to the formation of numerous polyps.
How Common Is FAP?
Familial Adenomatous Polyposis affects approximately 1 in 7,000 to 10,000 people worldwide.
Although considered rare, FAP accounts for nearly 1% of all colorectal cancers.
Since it is inherited in an autosomal dominant pattern, each child of an affected parent has a 50% chance of inheriting the condition.
What Causes Familial Adenomatous Polyposis?
The primary cause is an inherited mutation in the APC gene.
Normally, the APC gene:
- Controls cell growth
- Prevents abnormal cell division
- Suppresses tumour formation
When the gene is mutated:
- Cells multiply uncontrollably.
- Hundreds or thousands of polyps develop.
- Over time, some polyps become cancerous.
About 75–80% of patients inherit the mutation from a parent.
Around 20–25% develop FAP because of a new (spontaneous) genetic mutation without any family history.
At What Age Does FAP Usually Appear?
Most people begin developing polyps between 10 and 20 years of age.
Typical timeline:
- Childhood: Usually no symptoms
- Ages 10–15: Small polyps start forming
- Ages 15–25: Hundreds of polyps may appear
- Ages 30–40: High risk of colorectal cancer if untreated
Because symptoms often appear late, screening family members before symptoms develop is extremely important.
What Are the Symptoms of Familial Adenomatous Polyposis?
Many people experience no symptoms during the early stages.
As the number of polyps increases, symptoms may include:
- Rectal bleeding
- Blood in stool
- Frequent diarrhea
- Constipation
- Changes in bowel habits
- Abdominal pain
- Unexplained weight loss
- Fatigue due to anaemia
Some people also develop symptoms outside the digestive system, including:
- Extra or missing teeth
- Jaw cysts
- Osteomas (benign bone growths)
- Skin cysts
- Eye pigment changes (CHRPE)
- Thyroid nodules
These findings can help doctors suspect FAP before bowel symptoms appear.
What Are the Two Types of FAP?
There are two main forms.
1. Classic Familial Adenomatous Polyposis
This is the more severe type.
Features include:
- More than 100 colorectal polyps
- Polyps appear during teenage years
- Nearly 100% lifetime colorectal cancer risk without surgery
2. Attenuated Familial Adenomatous Polyposis (AFAP)
This is a milder form.
Characteristics include:
- Fewer than 100 polyps
- Later onset
- Cancer develops later in life
- Lower, but still significant, cancer risk
What is the Gardner Syndrome?
Gardner syndrome is a subtype of Familial Adenomatous Polyposis.
In addition to colon polyps, people with Gardner syndrome develop:
- Osteomas (bone tumours)
- Epidermoid cysts
- Fibromas
- Dental abnormalities
- Desmoid tumours
- Soft tissue growths
Because of these additional features, Gardner syndrome may be diagnosed before bowel symptoms begin.
What Is Turcot Syndrome?
Another rare variant of FAP is Turcot syndrome.
It combines:
- Colon polyps
- Increased risk of brain tumours
Patients require careful monitoring by multiple specialists.
What Is the Lifetime Risk of FAP?
Without treatment:
- Nearly 100% lifetime risk of colorectal cancer
Cancer often develops before age 40.
FAP also increases the risk of several other cancers, including:
This is why lifelong screening is essential.
How Do You Test for Familial Adenomatous Polyposis?
Diagnosis usually involves several tests.
Colonoscopy
This is the most important diagnostic test.
Doctors look for:
- Numerous adenomatous polyps
- Size
- Number
- Location
Biopsies may be taken to evaluate abnormal tissue.
Genetic Testing
Blood samples are analysed for mutations in the APC gene.
Genetic testing:
- Confirms diagnosis
- Identifies affected family members
- Helps guide screening
Upper GI Endoscopy
Since FAP also affects the stomach and duodenum, upper endoscopy is recommended.
Imaging
- Desmoid tumours
- Abdominal masses
- Other complications
What Is the Blood Test for FAP?
There is no routine blood test that diagnoses FAP.
However, a genetic blood test is used to analyse DNA for mutations in the APC gene.
This test confirms whether an individual carries the inherited mutation responsible for Familial Adenomatous Polyposis.
Routine blood tests may also be performed to check for:
- Anaemia
- Iron deficiency
- Nutritional status
These tests help assess complications but do not diagnose FAP.
What Is the Minimum Number of Polyps to Diagnose FAP?
There is no single fixed number, but generally:
- 100 or more adenomatous polyps strongly suggest classic FAP.
- Fewer polyps with a confirmed APC mutation may indicate attenuated FAP.
Doctors consider:
- Family history
- Genetic testing
- Colonoscopy findings
- Age
- Number of polyps
All these factors help establish the diagnosis.
How Do You Treat Familial Adenomatous Polyposis?
Treatment focuses on preventing colorectal cancer.
Management usually includes:
Regular Surveillance
Frequent colonoscopies monitor:
- New polyps
- Polyp growth
- Early cancer
Medications
Some medications may reduce the number of polyps.
Examples include:
- NSAIDs such as sulindac
- COX-2 inhibitors in selected patients
However, medications cannot replace surgery.
Preventive Surgery
Since polyps continue increasing over time, surgery is considered the most effective treatment.
Lifelong Follow-Up
Even after surgery, patients need:
- Colon surveillance
- Upper GI endoscopy
- Thyroid screening
- Imaging when necessary
Is Surgery Needed for Polyposis Syndrome?
In most cases, yes.
Because the cancer risk is extremely high, preventive surgery is recommended before cancer develops.
The timing depends on:
- Number of polyps
- Size
- Degree of dysplasia
- Family history
- Age
- Symptoms
Your surgeon and gastroenterologist determine the most appropriate time.
What Is the Treatment of Choice for FAP?
The treatment of choice is prophylactic colectomy—surgical removal of the colon before cancer develops.
This approach dramatically reduces colorectal cancer risk.
Depending on the individual, surgery may include:
- Total colectomy
- Restorative procedures
- Ileorectal anastomosis
- Ileal pouch-anal anastomosis (IPAA)
What Is the Full Form of FAP Surgery?
The abbreviation FAP stands for Familial Adenomatous Polyposis—it is the name of the condition, not a surgical procedure.
The surgeries commonly performed for FAP include:
- Total colectomy (removal of the entire colon)
- Proctocolectomy (removal of the colon and rectum)
- Ileal Pouch-Anal Anastomosis (IPAA), where a pouch is created from the small intestine to preserve bowel function
- Subtotal colectomy with ileorectal anastomosis (IRA) in selected patients
The exact procedure depends on the number and location of polyps, rectal involvement, age, and overall health.
Can Lifestyle Changes Reduce FAP Risk?
Lifestyle changes cannot prevent or cure Familial Adenomatous Polyposis because it is caused by an inherited genetic mutation.
However, healthy habits may support overall digestive health and reduce the risk of other diseases.
Helpful lifestyle measures include:
- Eating a balanced, fibre-rich diet
- Maintaining a healthy weight
- Exercising regularly
- Avoiding smoking
- Limiting alcohol intake
- Following recommended screening schedules
- Taking prescribed medications if advised
- Keeping regular follow-up appointments
The most important step remains early diagnosis and timely medical treatment.
Can FAP Be Prevented?
The genetic mutation itself cannot be prevented.
However, families with a history of FAP can benefit from:
- Genetic counselling
- Genetic testing
- Early colonoscopy screening
- Screening of children at risk
- Preventive surgery when appropriate
These measures can prevent colorectal cancer even though they cannot prevent the inherited condition.
Living with Familial Adenomatous Polyposis
Receiving a diagnosis of FAP can feel overwhelming, but many people live full and healthy lives with proper care.
Successful management often involves a multidisciplinary team that may include:
- Gastroenterologists
- Colorectal surgeons
- Genetic counsellors
- Oncologists
- Dietitians
- Primary care physicians
Long-term follow-up and adherence to surveillance schedules are essential for maintaining good health and detecting any new issues early.
When Should You See a Doctor?
Seek medical advice if you experience:
- Persistent rectal bleeding
- Blood in stool
- Ongoing changes in bowel habits
- Unexplained abdominal pain
- Unintentional weight loss
- A family history of FAP or early colorectal cancer
Early evaluation can make a significant difference in outcomes.
Frequently Asked Questions (FAQ)
1. What is a familial adenomatous polyposis?
Familial Adenomatous Polyposis (FAP) is a rare inherited condition caused by mutations in the APC gene. It leads to the development of hundreds or thousands of colorectal polyps and carries a very high risk of colorectal cancer if left untreated.
2. What is the Gardner syndrome?
Gardner syndrome is a subtype of FAP that includes colon polyps along with bone tumours (osteomas), skin cysts, dental abnormalities, and soft tissue growths.
3. What is the full form of FAP surgery?
FAP stands for Familial Adenomatous Polyposis and is not the name of a surgery. Surgical treatment typically involves procedures such as total colectomy, proctocolectomy, or ileal pouch-anal anastomosis (IPAA), depending on the patient’s condition.
4. How do you treat familial adenomatous polyposis?
Treatment includes regular colonoscopy surveillance, genetic counselling, medications in selected cases, preventive colectomy, and lifelong monitoring of the digestive tract and other organs at increased cancer risk.
5. At what age does FAP usually appear?
Polyps usually begin developing between the ages of 10 and 20 years, although symptoms may not appear until later.
6. What are the two types of FAP?
The two main types are Classic Familial Adenomatous Polyposis and Attenuated Familial Adenomatous Polyposis (AFAP).
7. What is the blood test for FAP?
The primary blood test is genetic testing for APC gene mutations, which helps confirm the diagnosis and identify affected family members.
8. Is surgery needed for polyposis syndrome?
Yes. Most people with FAP eventually require preventive surgery because the lifetime risk of colorectal cancer is extremely high.
9. What is the treatment of choice for FAP?
The treatment of choice is prophylactic colectomy, combined with lifelong surveillance of the gastrointestinal tract.
10. What is the lifetime risk of FAP?
Without treatment, the lifetime risk of colorectal cancer is nearly 100%.
11. How do you test for familial adenomatous polyposis?
Diagnosis involves colonoscopy, APC genetic testing, upper gastrointestinal endoscopy, family history assessment, and imaging when necessary.
12. What is the minimum number of polyps to diagnose FAP?
Classic FAP is generally suspected when 100 or more adenomatous colorectal polyps are present. However, fewer polyps with a confirmed APC mutation may indicate attenuated FAP.
13. Can lifestyle changes reduce FAP risk?
Lifestyle changes cannot eliminate the inherited genetic risk, but healthy habits, avoiding smoking, maintaining a healthy weight, and following recommended screening and treatment plans can support overall health and improve long-term outcomes.
Familial Adenomatous Polyposis is a serious but manageable inherited condition. While the diagnosis can be life-changing, modern medicine offers highly effective ways to reduce cancer risk through early detection, genetic testing, regular surveillance, and preventive surgery.
If you have a family history of colorectal cancer or hereditary polyposis syndromes, don’t ignore the warning signs. Early screening and timely intervention can be lifesaving. With the right medical care and ongoing follow-up, individuals with FAP can significantly reduce their cancer risk and enjoy a better quality of life.
To consult a Doctor or get full body check-up done at Sparsh Diagnostic Centre, call our helpline numbers 9830117733/ 8335049501.
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