Familial Adenomatous Polyposis (FAP) | Loyola Medicine

Familial Adenomatous Polyposis (FAP)

Overview and Facts about Familial Adenomatous Polyposis

Familial adenomatous polyposis (FAP) is a rare, hereditary condition in which polyps form in the large intestine, rectum and upper digestive tract. An adenomatous polyp develops when normal cells inside the gastrointestinal tract mutate and form a small tissue mass; a FAP diagnosis is made when a person has hundreds, even thousands of adenomatous polyps.

Left untreated, people with FAP risk developing colorectal cancer. Cancer of the stomach, small intestine, pancreas, and liver can also plague people with FAP. If polyps cannot be managed, FAP patients may require surgical removal of the large intestine in order to prevent cancer.  

Signs and Symptoms of Familial Adenomatous Polyposis

In FAP, symptoms typically appear only when the polyps that have formed have become cancerous. Signs and symptoms of FAP and colorectal cancer include:

  • Blood or mucus in the stool
  • Rectal bleeding
  • Rectal pain
  • Diarrhea
  • Constipation
  • Abdominal pain
  • Weight loss

Causes and Risk Factors of Familial Adenomatous Polyposis

The primary risk factor for FAP is having a family member with the condition. FAP is caused by a genetic mutation to the adenomatous polyposis coli gene. While the genetic abnormality is typically passed down from a parent, a quarter of cases develop the mutation spontaneously.

Besides the risk of developing of cancer, FAP can also cause other complications, including digestive health issues, polyps in different parts of the body, desmoids (noncancerous tumors in the stomach), noncancerous tumors of the skin and bone, changes to the pigment in the eye’s retina and thyroid and dental issues.

Tests and Diagnosis of Familial Adenomatous Polyposis

If FAP runs in the family, regular screening for polyps is extremely important and should start in childhood. At-risk children will usually undergo genetic testing to determine the presence of the adenomatous polyposis coli gene. Screening tests used to monitor FAP and its complications include colonoscopy, sigmoidoscopy and upper endoscopy techniques, in which a flexible tube is inserted into the colon, esophagus or stomach. Imaging tests such as CT and MRI scans may be used to confirm tumors in the stomach, and ultrasound can monitor the thyroid.

Treatment and Care for Familial Adenomatous Polyposis

Small polyps detected during a colonoscopy can be removed at the same time; however, FAP patients typically develop too many polyps to remove them all individually. To prevent the polyps from becoming cancerous, surgery may be recommended. In this, parts of the stomach, small intestine or colon will be removed or reconstructed. Unfortunately, surgery does not cure FAP, and polyps may continue to develop.

FAP surgery can use minimally invasive techniques, such as laparoscopic surgery, which involves a few small incisions in the abdomen through which the procedure is performed. More extensive procedures to treat FAP include:

  • Ileal pouch-anal anastomosis (J-pouch surgery), which involves removing both the colon and rectum
  • A total colectomy, or removing the colon but preserving the rectum
  • A continent ileostomy, which is connecting the small intestine to an opening outside of your body.