MUTYH-Associated Polyposis (MAP)

At a glance…

• Children have a 1 in 4 chance of developing MAP if both parents are carriers
• Caused by changes in the MUTYH gene, inherited from both parents
• Leads to multiple bowel polyps, usually fewer than in FAP
• Increases risk of bowel cancer if untreated
• Parents who each carry one copy are “carriers” and usually have no symptoms

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

MAP is a genetic condition where people develop multiple adenomatous polyps in the bowel. It increases the risk of bowel cancer if polyps are not carefully monitored and managed. Usually, people with MAP develop fewer polyps than in FAP.
MAP is inherited differently to most other syndromes: it happens when both parents carry a change in the same gene. This means other family members may be “carriers” without having the condition themselves.

What symptoms to look out for

What symptoms to look out for

• Blood in your poo
• Tummy pain or bloating
• Changes in your bowel habit
• Anaemia (tiredness or pale skin)

Sometimes, MAP is diagnosed before symptoms appear, thanks to genetic testing.

About the gene differences

MAP is caused by changes in the MUTYH gene. This gene usually helps the body repair damage to DNA. When it does not work properly, polyps and cancers can develop.

How it runs in families

MAP is inherited in an “autosomal recessive” way. This means:

• You need to inherit the gene difference from both parents to develop MAP.
• Parents who each carry one copy are called “carriers.” Carriers do not usually develop MAP themselves.
• If both parents are carriers, each child has a 1 in 4 chance of developing MAP.

How it is diagnosed

• Colonoscopy to check for polyps
• Genetic testing for differences in the MUTYH gene
• Family history and genetic counselling

Screening and treatment

• Regular colonoscopies and polyp removal
• Screening for other cancers in some cases
• Ongoing monitoring of the bowel and digestive system

Possible surgery options

If polyps become too numerous, surgery may be recommended to remove the colon and sometimes the rectum. This greatly reduces cancer risk.

Health and lifestyle tips

• Stick to your screening schedule
• Eat a balanced diet with fibre-rich foods
• Exercise regularly and avoid smoking
• Share your family history with your healthcare team

Planning a family

Because MAP is recessive, genetic counselling is especially important. If your partner is a carrier of MUTYH, your children may be at risk. Testing can help you understand your options before or during pregnancy.