Colorectal Cancer - Familial Adenomatous Polyposis (FAP)
Colorectal Cancer Familial Adenomatous Polyposis (FAP) Mutations Detection of apc gene
FAP is an inherited colorectal cancer syndrome and accounts for 1 percent of all cases of colorectal cancer. The “F” stands for familial, meaning it runs in families; “A” stands for adenomatous, the type of polyps detected in the colon and small intestine that can turn into cancer; and “P” stands for polyposis, or the condition of having lots of colon polyps. Patients with FAP develop hundreds to thousands of colon polyps, usually starting in the teens. All patients will develop colorectal cancer from the colon polyps usually by age 40. Patients with FAP must have the colon, and sometimes the rectum, removed to prevent colon cancer.
Since the abnormal gene that causes FAP is present in all of the body’s cells, other organs may develop growths.
A significant breakthrough in the diagnosis of FAP was made with the discovery of the gene on chromosome 5. Now, family members at risk of FAP may have their blood taken and analyzed for the FAP gene mutation (called APC).
There are two widely used methods for detecting mutations: One is a protein truncation test, and the other is direct DNA sequencing. Gene testing should first be done on a family member with FAP. If the mutation is found, other family members can be tested. If the mutation is not found, blood testing is not helpful to test family members to see if they have FAP.