Familial Adenomatous Polyposis (FAP)

Familial adenomatous polyposis (FAP) is a rare, inherited disorder characterized by the development of hundreds to thousands of polyps in the colon and rectum. These polyps are typically benign (non-cancerous), but they have a high potential to become malignant (cancerous) over time.

Causes and Risk Factors

FAP is caused by a mutation in the APC gene, which is responsible for regulating cell growth and division. This mutation leads to the formation of multiple adenomatous polyps in the colon and rectum. The condition is inherited in an autosomal dominant pattern, meaning that a single copy of the mutated gene is enough to cause the disorder.

Symptoms

The symptoms of FAP may include:

• Blood in the stool or black, tarry stools
• Diarrhea or constipation
• Abdominal pain or cramping
• Weight loss or fatigue
• Anemia (low red blood cell count)

Diagnosis

The diagnosis of FAP is typically made through a combination of the following tests:

• Colonoscopy: a procedure that uses a flexible tube with a camera to visualize the inside of the colon and rectum
• Genetic testing: a blood test that checks for mutations in the APC gene
• Biopsy: a procedure that removes a sample of tissue from a polyp for examination under a microscope

Treatment

The treatment of FAP typically involves:

• Surgical removal of the colon and rectum (colectomy) to prevent cancer from developing
• Regular surveillance with colonoscopy to monitor for new polyps or cancer
• Removal of polyps (polypectomy) during colonoscopy

Complications

If left untreated, FAP can lead to the development of colorectal cancer. Other complications may include:

• Intestinal obstruction or blockage
• Bleeding or anemia from polyps
• Malnutrition or weight loss due to malabsorption

Prevention

There is no way to prevent FAP, but regular surveillance and early treatment can help reduce the risk of complications. Individuals with a family history of FAP should undergo genetic testing and regular colonoscopy screenings starting at a young age.

Frequently Asked Questions (FAQs)

What is Familial Adenomatous Polyposis (FAP)?
A rare inherited disorder characterized by the development of hundreds to thousands of polyps in the colon and rectum.

What are the symptoms of FAP?
Typically asymptomatic until polyps become numerous, then may include bleeding, diarrhea, abdominal pain, and weight loss.

How is FAP diagnosed?
Through genetic testing, endoscopy, and biopsy to identify mutations in the APC gene and presence of adenomatous polyps.

What is the risk of colorectal cancer in FAP patients?
Nearly 100% if left untreated, due to the high number of adenomatous polyps that can become malignant over time.

Can FAP be treated with medication?
No, treatment typically involves surgical removal of the colon and rectum to prevent cancer development.

Is FAP inherited in an autosomal dominant pattern?
Yes, meaning a single copy of the mutated APC gene is sufficient to cause the condition.

What are the extra-colonic manifestations of FAP?
May include osteomas, desmoid tumors, and congenital hypertrophy of the retinal pigment epithelium (CHRPE).

Can FAP increase the risk of other cancers?
Yes, may also increase the risk of other cancers such as gastric, duodenal, and thyroid cancer.

Is genetic counseling recommended for families with a history of FAP?
Yes, to identify family members who may be at risk and provide guidance on screening and management options.

What is the age range for FAP diagnosis?
Typically diagnosed between 10-30 years old, although symptoms may not appear until later in life.