Familial Adenomatous Polyposis (FAP)

What is familial adenomatous polyposis (FAP)?

Familial adenomatous polyposis (FAP) is a rare condition in which extra tissue, called polyps, forms in the large intestine, rectum, and/or upper gastrointestinal tract.  Hundreds or even thousands of these polyps can form by the mid-teens, and if these polyps are left untreated, they almost certainly can lead to cancer by age 40.

What causes familial adenomatous polyposis (FAP)?

FAP is caused by a defect in the adenomatous polyposis coli (APC) gene that is inherited from a parent in an autosomal dominant manner. However, in 25 percent of FAP cases, this genetic mutation occurs spontaneously.

What are the symptoms of familial adenomatous polyposis (FAP)?

FAP is characterized by hundreds to thousands of colorectal adenomatous polyps, which develop on average at 16 years of age. Besides these polyps, the follow extracolonic manifestations can also be present in FAP:

• Polyps in the stomach, duodenum, small bowel
• Osteomas (bony growths)
• Dental abnormalities
• Congenital hypertrophy of the retinal pigment epithelium (CHRPE)
• Soft tissue tumors

How is familial adenomatous polyposis (FAP) diagnosed?

A clinical evaluation and patient history are the first steps to a diagnosis of FAP. One of two qualifications must be observed from this for a FAP diagnosis to be made: a patient must have 100 or more of the adenomatous colorectal polyps, or they may have fewer than 100 polyps but a relative with FAP. Genetic testing to determine a mutated APC gene is available to confirm a diagnosis.

What are the available treatments for familial adenomatous polyposis (FAP)?

The primary treatment for FAP is a surgery to completely or partially remove the colon, called a colectomy. After this surgery, if there are remaining polyps, a drug called Sulindac (a nonsteroidal anti-inflammatory drug) can be taken to regress them. Any other polyps that have grown should also be surgically removed, whether in the stomach, duodenum, or small bowel. After these surgeries, FAP patients should be monitored for cancer.

Where can I find more information on familial adenomatous polyposis (FAP)?

• Mayo Clinic
• NIH
• National Organization for Rare Disorders (NORD)