Familial adenomatous polyposis (FAP) syndrome is a genetic syndrome that predisposes individuals to develop hundreds to thousands of adenomatous polyps, in addition to colorectal cancer, papillary thyroid cancer and other cancers. Every patient with FAP will develop colorectal cancer, typically by age 40, unless screening and preventive measures are taken.
In childhood, patients with FAP are at risk for developing:
- Hepatoblastoma (a type of liver cancer), typically before age 5
- Medulloblastoma (a type of brain cancer)
- Thyroid cancer
- Gastrointestinal (especially colorectal) polyps
- Desmoid tumors (typically noncancerous)
- Extra/additional teeth
What are the causes?
FAP is caused by inherited genetic changes in the APC gene. A child of a parent diagnosed with FAP has a 50% chance of inheriting this condition. While the majority of cases are passed down to a child from a parent, nearly 20% of cases of FAP occur for the first time in the affected child and are not inherited.
The incidence of FAP is estimated to be 1 in 14,000.
How is familial adenomatous polyposis diagnosed?
FAP can be diagnosed through genetic testing, which is typically performed by a genetic counselor.
Family history of polyposis, “carpeted colon” appearance on a colonoscopy or colon cancer diagnosed at very early ages (20s to 40s) can also increase the likelihood of this diagnosis.
Treatment and monitoring
Guidelines and recommendations exist for the care and surveillance of children and adults with FAP.
- Annual colonoscopy screening beginning between ages 10 and 15
- Cervical palpation of thyroid
- Abdominal ultrasound and labs
- Annual physical exam by pediatric hematologist/oncologist with expertise in caring for patients with FAP