Familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is an inherited condition in which numerous adenomatous polyps form mainly in the epithelium of the large intestine. While these polyps start out benign, malignant transformation into colon cancer occurs when they are left untreated. Three variants are known to exist, FAP and attenuated FAP (originally called “hereditary flat adenoma syndrome) are caused by APC gene defects on chromosome 5 while autosomal recessive FAP (or MYH-associated polyposis) is caused by defects in the MUTYH gene on chromosome 1. Of the three, FAP itself is the most severe and most common; although for all three, the resulting colonic polyps and cancers are confined to the colon wall and removal can greatly reduce the spread of cancer.