FAP FAQs

What is FAP?
Familial adenomatous polyposis (FAP) is an inherited condition in which numerous benign growths, or polyps, form mainly in the inner lining of the large intestine (the colon and rectum). If the colon is not removed, these polyps almost always become malignant by the age of 40.

What are the symptoms of FAP?
Beginning in early adolescence, patients with FAP develop hundreds to thousands of polyps. These may cause blood in the stool, anemia (low blood counts) due to blood loss, weight loss and/or altered bowel habits.

What causes FAP?
There are two main genetic defects responsible for FAP.

The most common form of the disease is caused by a mutation in the APC (adenomatous polyposis coli) gene. APC normally acts as a “tumor suppressor” that limits unchecked cell growth. Except for sperm and eggs, every cell in our bodies has two copies of the gene – one inherited from each parent. You only have to inherit one copy of the mutant APC gene to have the disease, meaning this mutation is “autosomal dominant.”

FAP can also be caused by mutations in another gene, called MUTYH (MYH glycosylase). The gene encodes a protein that repairs DNA damage that happens during normal cellular activities. Mutations in the MUTYH gene are inherited in an “autosomal recessive” pattern, which means two copies of the gene must be altered for a person to be affected by the disorder.

How common is FAP?
FAP is rare, accounting for only about 1 percent of colorectal cancer cases. Estimates range from 1 in 7,000 to 1 in 22,000.

How do I find out if I have FAP?
It is important to know your family history, i.e., if a close family member has had FAP or colon cancer. There are now several blood tests that can tell you if you have inherited one of the mutations that cause FAP. If FAP is suspected based on your symptoms or genetic background, a colonoscopy or other colon imaging studies should be done to look for polyps or tumors.

How is FAP treated?
To prevent colon cancer from developing, the colon must be surgically removed by a procedure called a colectomy. Certain drugs (e.g., celecoxib and sulindac) may also be used following surgery to reduce the number and size of polyps in the rectum. After the colon is removed, regular screenings to check for polyp recurrence in the rectum are required.