Familial adenomatous polyposis

Types

Familial adenomatous polyposis has these variations:

• Attenuated familial adenomatous polyposis causes fewer polyps than classic familial adenomatous polyposis, usually less than 100. You have a high likelihood of developing colon cancer by age 60 if the polyps are not removed.
• Gardner's syndrome is a form of familial adenomatous polyposis that also causes bony and dental growths.

MYH-associated polyposis (MAP)

This rare genetic disorder is caused by a different gene (the MYH gene), but has similar colon and duodenum risks. The number of polyps can vary, with up to 40 percent of people with MAP having 10 to 100 polyps, and up to 30 percent having more than 100 polyps. The risk of developing colon cancer is estimated to be 80 percent by age 70, if the polyps cannot be controlled with colonoscopy or if the colon and rectum are not removed.

At Mayo Clinic, people with MAP have colonoscopies every year, beginning at age 25.