APC Inherited Mutations

Information for People with Inherited APC Mutations

People with a mutation in the APC gene have an increased risk for cancer, particularly, colorectal cancer. The lifetime cancer risks and risk management recommendations depend on several factors, including the location and type of APC mutation. APC mutations and their related cancer risks are typically divided into 3 categories:

• Familial adenomatous polyposis (FAP)
• Attenuated FAP
• APC variant I1307K

Familial adenomatous polyposis (FAP) and attenuated FAP (AFAP)

FAP and AFAP are caused by mutations in the APC gene. These conditions are rare, occurring in about one in 10,000 people. People with FAP may develop hundreds to thousands of in their colon and rectum, often beginning in their teenage years or early adulthood. Attenuated FAP is a milder subset of FAP that tends to begin at a later age than FAP. People with AFAP may develop dozens rather than hundreds or thousands of colon and rectal polyps. Risk management recommendations for people with FAP and AFAP begin at a young age and continue throughout their life.

APC variant I1307K

A variant in the APC gene, known as I1307K (or sometimes called c.3920T>A or p.Ile1307Lys) is common in people of Eastern European Jewish ethnicity; about 7 percent will have this variant. People who test positive for I1307K do not develop FAP. They do have a slightly increased risk for colorectal cancer beginning in adulthood and risk management recommendations include more frequent screenings beginning at a slightly younger age than people in the general population.

There may be other medical concerns for people with a APC mutation, including cancer risks for children beginning at a young age.

Each of these topics is outlined in more detail in the sections highlighted below. 

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