Familial Adenomatous Polyposis (FAP)

What isĀ Familial Adenomatous Polyposis?

Familial adenomatous polyposis is a genetically inherited condition. It primarily affects the colon and rectum. This condition occurs due to changes in one of two genes, the APC or the MUYTH gene. When the mutation occurs in the APC gene, it is a dominant condition, meaning that one copy of the cell is mutated and most often that one parent carries the gene. If the condition occurs because of the MUYTH gene, it is considered to be a recessive condition and both copies of the gene are mutated. Most often this means both parents are carriers of the mutation.

When a person has familial adenomatous polyposis, they tend to grow polyps which are growths or small nodules inside of the colon as early as during their teenage years. Polyps in the colon are usually benign but can sometimes be cancerous or become cancerous, and when a person has familial adenomatous polyposis, their polyps develop into colon and/or rectal cancer.

Familial adenomatous polyposis also makes a person more likely to develop cancer in the small intestine and stomach. In fact, adrenal cancer, liver cancer, and even pancreatic cancer occur more frequently in people with familial adenomatous polyposis than people who do not have the condition.

What are the Symptoms of Familial Adenomatous Polyposis?

Some of signs may be present at birth, like congenital defects in the eye, while others may not be noticed until later in life.

Symptoms include

Polyps, bony growths or tumors in the jaw, missing teeth or teeth that do not come in all the way, benign cysts on the skin, adrenal tumors, and congenital eye defects. Some of these signs maybe present at birth, like congenital defects in the eye, while others may not be noticed until later in life.

Familial Adenomatous Polyposis Causes

Familial Adenomatous Polyposis is caused by a malfunction in the adenomatous polyposis coli (APC) gene. This genetic abnormality is generally inherited from a parent, but in about 25% of all cases, the genetic mutation occurs spontaneously. This abnormal gene causes hundreds of polyps to develop in an affected person’s colon and rectum. In people with classic familial adenomatous polyposis, the number of polyps increases significantly with age. Polyps begin occurring around the teenage years and become cancerous by age 40 in almost all cases. It can be inherited from parents in one of two ways. A mutation in the APC gene is inherited in an autosomal dominant pattern. In these cases, typically only one parent is a carrier for the genetic mutation and one copy of the gene is enough to cause the disease. If, however, there is a mutation in the MUTYH gene, then it is inherited in an autosomal recessive pattern. In this case, both parents are typically carriers for the genetic mutation, although they do not show signs or symptoms of the disease themselves. When a child inherits two copies of the mutated gene, familial adenomatous polyposis is likely to occur.

How is Familial Adenomatous Polyposis Treated?

The treatment for familial adenomatous polyposis depends on the severity of the condition and the extent of it.

Treatment includes

Close care and monitoring will be vital throughout childhood and into adulthood. When polyps are found, they need to be removed and biopsied to determine if they are cancerous.

If more than 20 polyps are present in the colon, doctors often recommend a colectomy to remove the colon entirely. This is designed to prevent colon cancer from developing. If a person with familial adenomatous polyposis has tumors elsewhere like in the thyroid or jaw, these need to be removed as well. And, of course, should familial adenomatous polyposis cause a person to develop cancer, chemotherapy, radiation, and other indicated cancer treatments will be necessary.

Familial Adenomatous Polyposis Prevention

Although familial adenomatous polyposis is generally caused by a genetic disorder passed from parent to child, there are strategies that one can take to avoid polyps turning cancerous. Non-steroidal anti-inflammatory drugs (NSAIDs) have been shown to be effective in regressing growth of polyps that grow in the colon, but less so in polyps that grow in different parts of the body, which most people with familial adenomatous polyposis eventually develop. Frequent monitoring is required, and a colectomy may be necessary to prevent the growth of additional polyps, as there exists a near-certain chance of eventual cancer.

Last Reviewed:
September 20, 2016
Last Updated:
December 21, 2017