Which are the causes of Familial Adenomatous Polyposis?

Familial Adenomatous Polyposis (FAP) is primarily caused by a germline mutation in the APC (Adenomatous Polyposis Coli) tumor suppressor gene. This genetic alteration prevents the body from effectively regulating cell growth in the colon, leading to the development of hundreds to thousands of precancerous polyps.

What causes Familial Adenomatous Polyposis?

The root cause of Familial Adenomatous Polyposis is a mutation in the APC gene located on chromosome 5q21. Think of the APC gene as the "brakes" for cell division in the lining of your colon. In individuals with Familial Adenomatous Polyposis, these brakes are faulty, allowing cells to multiply uncontrollably and form polyps. While most cases are inherited, approximately 25% of patients have a de novo mutation, meaning it occurred spontaneously in the individual without a family history.

Is Familial Adenomatous Polyposis hereditary?

Yes, Familial Adenomatous Polyposis follows an autosomal dominant inheritance pattern. This means if one parent carries the mutation, there is a 50% chance they will pass it on to each of their children. Because of this high inheritance rate, genetic counseling is a critical component for families affected by Familial Adenomatous Polyposis.

Are there environmental triggers or other factors?

While the primary driver of Familial Adenomatous Polyposis is genetic, researchers are actively studying how environment and metabolism influence the speed of polyp growth. Key factors include:

• Dietary habits: High-fat, low-fiber diets may potentially exacerbate polyp development.


• Inflammation: Chronic irritation within the gastrointestinal tract may impact the progression of polyps.


• Metabolic factors: Research is ongoing regarding how insulin levels and inflammation markers may interact with the APC mutation.

What is the difference between causes and risk factors?

In Familial Adenomatous Polyposis, the APC mutation is the cause; it is the absolute requirement for the disease to manifest. Risk factors, such as dietary choices or age, are external or secondary elements that may influence how quickly the disease progresses or the severity of the polyps, but they do not cause the condition itself.

Next steps

• Schedule a consultation with a clinical geneticist to discuss testing options for your family.


• Join our community at DiseaseMaps.org to connect with 147 other individuals living with Familial Adenomatous Polyposis.


• Consult a gastroenterologist specializing in hereditary colorectal cancer syndromes for regular surveillance.

Medical disclaimer: This content is for educational purposes only and should not replace professional medical advice, diagnosis, or treatment.

References

• NIH Genetic and Rare Diseases Information Center (GARD): Familial Adenomatous Polyposis.


• Orphanet: Familial Adenomatous Polyposis (ORPHA:734).


• OMIM (Online Mendelian Inheritance in Man): Adenomatous Polyposis of the Colon (Entry #175100).


• The Colon Cancer Foundation: Educational resources on APC-related polyposis.