Familial Adenomatous Polyposis (FAP)

At a glance…

• Rare inherited condition caused by a change in the APC gene
• Usually starts in the teenage years with hundreds of bowel polyps
• Very high risk of bowel cancer if not treated
• Regular screening and sometimes surgery can prevent cancer
• Each child of an affected parent has a 50% chance of inheriting FAP

What the syndrome is and what it means for you and your family

FAP is a rare inherited condition where many polyps develop in the bowel, usually starting in the teenage years. If untreated, these polyps will almost always turn into bowel cancer. The good news is that with regular screening and treatment, cancer can usually be prevented.

FAP can affect the whole family, because it is an inherited condition. If you have FAP, close relatives may also carry the gene difference and can be offered testing and support.

What symptoms to look out for

Not everyone with FAP will have symptoms at first, but possible signs include:

• Blood in your poo
• Changes in your bowel habit (such as diarrhoea or constipation that does not go away)
• Tummy pain or bloating
• Unexplained tiredness (from anaemia)

Because symptoms may not appear until later, regular screening is the safest way to manage FAP.

About the gene differences

FAP happens because of a difference in a gene called APC. Genes act like instructions for how the body works. When the APC gene does not work as expected, polyps can form in the bowel and other parts of the digestive system.

How it runs in families

FAP is passed on in families in an “autosomal dominant” way. This means that if one parent has FAP, there is a 50% chance their child will inherit it. Both men and women can pass it on.

Because of this, genetic testing and counselling are often recommended for family members.

How it is diagnosed

• Colonoscopy (a camera is passed through the bowel) to look for polyps.
• Genetic testing to check for a difference in the APC gene.
• Family history can be a clue if other relatives have had polyps or bowel cancer at a young age.

Screening and treatment

If you have FAP, you will usually have:

• Regular colonoscopies to check the bowel and remove polyps.
• Monitoring of the stomach and small intestine, as polyps can also appear there.
• Screening for other health risks linked to FAP, such as thyroid problems.

Possible surgery options

If there are too many polyps to manage safely with colonoscopy, surgery may be advised. This may involve:

• Removing the colon (colectomy), sometimes with the rectum as well.
• Different surgical techniques may be discussed with you depending on your age, number of polyps, and overall health.

Although surgery can sound daunting, it is usually very effective at reducing cancer risk.

Health and lifestyle tips

• Healthy eating: A balanced diet with plenty of fruit, vegetables, and fibre supports bowel health.
• Stay active: Regular movement helps digestion and overall wellbeing.
• Avoid smoking and limit alcohol: These increase cancer risk.
• Keep up with check-ups: The most important step you can take is sticking with your regular screening.

Planning a family

If you are thinking about having children, you may want to talk with a genetic counsellor. Options such as testing during pregnancy or before IVF (pre-implantation genetic testing) can give families choices about passing on FAP.