Familial Adenomatous Polyposis – Symptoms and Causes
Understanding Familial Adenomatous Polyposis
Familial adenomatous polyposis (FAP) is an inherited condition resulting from a defect in the adenomatous polyposis coli (APC) gene. About 25-30% of cases occur as new genetic mutations.
This condition causes polyps to develop in the large intestine and rectum. These growths can also appear in the upper digestive tract, particularly in the duodenum (upper small intestine).
Without treatment, these polyps typically become cancerous by the time a person reaches their 40s.
Symptoms
People with familial adenomatous polyposis (FAP) develop hundreds to thousands of polyps in their colon and rectum, typically starting during the teenage years.
These polyps are small growths on the inner lining of the large intestine. Most polyps start as tiny bumps smaller than peas, but can grow larger over time.
Many people with FAP don’t notice symptoms in the early stages. As polyps increase in number and size, they may experience:
- Blood in the stool
- Diarrhea or frequent bowel movements
- Abdominal pain or cramping
- Mucus discharge from the rectum
- Unexplained weight loss
FAP can also cause growths outside the colon. These might include:
- Polyps in the upper digestive tract (stomach and small intestine)
- Cysts or tumors in the skin, bones, or other soft tissues
- Harmless changes in the retina of the eye
Some people develop a milder form called attenuated FAP, with fewer polyps that develop later in life.
Causes
Familial adenomatous polyposis (FAP) happens because of changes in a person’s genes. Most cases stem from mutations in the APC gene, which normally helps prevent tumors. This gene mutation is usually passed down from parents to children.
People with FAP inherit one defective copy of the APC gene from a parent. Each child of someone with FAP has a 50% chance of getting the condition.
Some people (about 25-30%) develop FAP without any family history, which means the gene mutation occurred randomly.
The APC gene normally controls cell growth. When it’s damaged, cells in the colon lining grow too much, forming hundreds or thousands of polyps. These polyps start appearing during teenage years and will almost certainly become cancerous if not treated.
Several types of FAP exist:
- Classic FAP: Hundreds to thousands of polyps develop.
- Attenuated FAP: Fewer polyps that appear later in life.
- Gardner syndrome: FAP plus growths outside the colon.
- Turcot syndrome: FAP with brain tumors.
Risk Factors
Several factors can increase the chance of developing familial adenomatous polyposis (FAP). The most significant risk factor is having a family history of this condition.
Age is another consideration. While FAP is typically diagnosed between ages 10 and 30, polyps can begin forming during childhood. Doctors often recommend that children from families with FAP begin screening around age 10-12.
Some people develop an attenuated form of FAP with fewer polyps that develop later in life. This variation still increases cancer risk but may be harder to detect early without proper screening.
Complications
Familial adenomatous polyposis (FAP) can lead to several serious health problems if not properly managed.
The most significant risk is the development of colorectal cancer, which occurs in nearly all untreated patients by age 40-50. When polyps turn cancerous, they can spread to other parts of the body, making treatment more difficult.
Beyond colorectal cancer, FAP can cause complications in other parts of the digestive system. Polyps may form in the stomach and small intestine, particularly the duodenum. These duodenal polyps carry a 5-12% lifetime risk of becoming cancerous.
People with FAP might develop desmoid tumors, which are noncancerous growths that occur in about 10-20% of patients. Though not malignant, these tumors can grow aggressively and cause problems by pressing against vital organs or structures.
Other possible complications include:
- Dental Abnormalities: Extra or missing teeth.
- Osteomas: Benign bone growths, often on the skull or jaw.
- Congenital Hypertrophy of Retinal Pigment Epithelium (CHRPE): Eye changes that don’t affect vision.
- Hepatoblastoma: A rare liver cancer that may affect children with FAP.
After surgical removal of the colon, patients may experience changes in bowel function and may need to adjust to new bathroom routines.
Prevention
Avoiding familial adenomatous polyposis (FAP) completely is not possible since it’s an inherited genetic condition. People born with the APC gene mutation will develop this condition. However, several steps can help manage risks and prevent serious complications.
Regular screening is crucial for those with a family history of FAP. Children with affected parents should begin colonoscopy screenings around ages 10-12. These screenings help doctors find polyps early before they become cancerous.
Genetic testing offers valuable information for at-risk families. Testing can identify who carries the mutation, allowing for proper monitoring and treatment plans. Family members who don’t have the mutation won’t need the intensive screening schedule.
Some preventive surgical options exist for FAP patients. Many doctors recommend removal of the colon (colectomy) once a person develops numerous polyps. This significantly reduces colon cancer risk. However, regular checkups remain important for other parts of the digestive tract.
Medications like nonsteroidal anti-inflammatory drugs (NSAIDs) may help slow polyp growth in some cases. Research suggests these medications can reduce polyp numbers and size. However, they don’t replace the need for regular screening or surgery when indicated.
Healthy lifestyle choices support overall well-being for FAP patients. A balanced diet rich in fruits and vegetables, regular exercise, avoiding tobacco, and limiting alcohol may improve general health outcomes. However, they don’t prevent the condition itself.
