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Familial Adenomatous Polyposis Syndrome

Last updated Sept. 11, 2018

Approved by: Krish Tangella MD, MBA, FCAP

Familial Adenomatous Polyposis Syndrome is a genetic disorder that increases an individual’s chance of developing colon cancer.


What are the other Names for this Condition? (Also known as/Synonyms)

  • Adenomatous Polyposis Coli
  • Hereditary Polyposis Coli
  • MYH-associated Polyposis

What is Familial Adenomatous Polyposis Syndrome? (Definition/Background Information)

  • Familial Adenomatous Polyposis Syndrome is a genetic disorder that increases an individual’s chance of developing colon cancer
  • There are two types of Familial Adenomatous Polyposis Syndrome: Classical Familial Adenomatous Polyposis Syndrome and Attenuated Familial Adenomatous Polyposis Syndrome
  • With Classical Familial Adenomatous Polyposis Syndrome, colon polyps usually occur in adolescents
  • Most of the polyps that develop are adenomatous polyps, which increase the chance of developing colon cancer
  • These adenomatous polyps are initially benign (harmless), but can become malignant (cancerous) if not treated
  • On an average, an individual with Familial Adenomatous Polyposis Syndrome develops colon cancer by age 39. Such individuals also develop a tumor of fibrous tissue called a desmoid tumor 
  • The incidence of Familial Adenomatous Polyposis Syndrome varies according to different studies. Some studies estimate the incidence to be 1 per 1000, whereas others estimate the incidence to be 1 per 22000
  • A variant of Familial Adenomatous Polyposis Syndrome can occur in an autosomal recessive type mutation inheritance. Individuals with Autosomal Recessive Familial Adenomatous Polyposis Syndrome have fewer colon polyps compared to individuals with Classical Familial Adenomatous Polyposis Syndrome 
  • The genetic abnormalities that are usually seen in the classical type are not seen in the autosomal recessive type of Familial Adenomatous Polyposis Syndrome
  • Familial Adenomatous Polyposis Syndrome is caused by a mutation in a gene called APC.
  • The majority of individuals do not exhibit signs or symptoms until they develop colon cancer
  • A family history and genetic testing is usually used to detect a mutation in the APC gene and diagnose Familial Adenomatous Polyposis Syndrome
  • The possible complications of Familial Adenomatous Polyposis Syndrome are the development of colon cancer in the polyps
  • The treatment of Familial Adenomatous Polyposis Syndrome usually includes the prophylactic removal of colon (prophylactic colectomy). Since Familial Adenomatous Polyposis Syndrome is a genetic disorder, there are currently no methods to prevent it

Who gets Familial Adenomatous Polyposis Syndrome? (Age and Sex Distribution)

  • The Familial Adenomatous Polyposis Syndrome occurs in individuals who have APC gene mutation or mutations in MUTYH gene
  • This syndrome can occur in both males and females
  • Familial Adenomatous Polyposis Syndrome can be seen in all ethic groups and races

What are the Risk Factors for Familial Adenomatous Polyposis Syndrome? (Predisposing Factors)

The risk factors of Familial Adenomatous Polyposis Syndrome include:

  • A family history of Familial Adenomatous Polyposis Syndrome, including parents, brothers, and sisters affected by the disease, is a very important risk factor
  • Mutation of tumor suppressor gene APC in either parent increases the risk

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others. 

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Familial Adenomatous Polyposis Syndrome? (Etiology)

The common causes of Familial Adenomatous Polyposis Syndrome include:

  • Familial Adenomatous Polyposis Syndrome is caused by a genetic mutation
  • In the majority of cases, this is a mutation in the APC tumor suppressor gene that is located on chromosome 5 at band q21. This mutation is inherited in an autosomal dominant fashion
  • There is a variant form of Familial Adenomatous Polyposis Syndrome that can occur when there are mutations in the MUTYH gene. In this scenario, the inheritance pattern is autosomal recessive, which means that both chromosomes should possess a genetic defect. The MUTYH gene encodes a DNA repair enzyme called MYH glycosylase 

Autosomal dominant: Autosomal dominant conditions are traits or disorders that are present when only one copy of the mutation is inherited on a non-sex chromosome. In these types of conditions, the individual has one normal copy and one mutant copy of the gene. The abnormal gene dominates, masking the effects of the correctly functioning gene. If an individual has an autosomal dominant condition, the chance of passing the abnormal gene on to their offspring is 50%. Children who do not inherit the abnormal gene will not develop the condition or pass it on to their offspring.

Autosomal recessive: Autosomal recessive conditions are traits or disorders that occur when two copies of an abnormal gene have been inherited on a non-sex chromosome. If both parents have an autosomal recessive condition, there is a 100% likelihood of passing on the mutated genes to their children. If, however, only one mutant copy of the gene is inherited, the individual will be a carrier of the condition but will not show any symptoms. Children born to two carriers have a 25% chance of being homozygous dominant (unaffected), a 50% chance of being heterozygous (carrier), and a 25% chance of being homozygous recessive (affected).

What are the Signs and Symptoms of Familial Adenomatous Polyposis Syndrome?

The signs and symptoms of Familial Adenomatous Polyposis Syndrome include:

  • In the majority of individuals affected by Familial Adenomatous Polyposis Syndrome, there are no signs or symptoms unless they develop colon cancer    
  • The signs and symptoms of colon cancer include:   
    • Rectal bleeding
    • Anemia
    • Diarrhea
    • Abdominal pain
    • Unexplained weight loss
    • Change in bowel habits
  • Individuals with Familial Adenomatous Polyposis Syndrome also have congenital hypertrophy of the pigmented epithelium of the retina. This finding can be detected by an ophthalmologist by looking at the retina using an ophthalmoscope
  • Individuals with Familial Adenomatous Polyposis Syndrome may also develop a fibrous tumor called a desmoid tumor. This tumor can cause abdominal mass in young individuals

How is Familial Adenomatous Polyposis Syndrome Diagnosed?

The following is the diagnostic methods for Familial Adenomatous Polyposis Syndrome:

  • The Familial Adenomatous Polyposis Syndrome is diagnosed based on the family history of the condition
  • Having close blood relatives increases the chances of developing Familial Adenomatous Polyposis Syndrome. The genetic testing for the mutation in the APC gene or in the MUTYH gene helps with a definitive diagnosis
  • APC gene mutation is found in 80% of individuals diagnosed with the syndrome
  • It is important to note that the presence of an APC gene mutation does not mean that an individual has colon cancer. It only indicates that the individual has a higher risk of developing colon cancer
  • A Screening Colonoscopy with biopsy can help determine the type of colon polyp present. If the colon polyps are of the adenomatous type, it can lead to malignancy
  • The greater the number of polyps in the colon, the greater the risk of developing colon cancer later in life
  • A Fecal occult blood test (FOBT) to detect blood in stool is an important screening tool to detect colon cancer. It is important to note that presence of blood in stool does not mean that the individual has colon cancer because blood may also be present in stool as a result of many non-cancer conditions Hence, a colonoscopy with a tissue biopsy is required to make a definitive diagnosis of colon cancer.
  • Double Contrast barium enema can determine presence of any tumors. The presence of tumors in the colon will appear as filling defects on the double Contrast barium enema. A radiologist performs this study

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Familial Adenomatous Polyposis Syndrome?

The following complications for Familial Adenomatous Polyposis Syndrome include:

  • The polyps can bleed, causing anemia
  • Adenomatous polyps can develop into colon cancer
  • Individuals diagnosed with Familial Adenomatous Polyposis Syndrome can also develop desmoid tumors, which can affect abdominal organs

How is Familial Adenomatous Polyposis Syndrome Treated?

The following treatments methods for Familial Adenomatous Polyposis Syndrome include:

  • Since Familial Adenomatous Polyposis Syndrome is a genetic disorder, there is no cure. The efforts to decrease the complications due the genetic defects by various methods are the treatment of choice
  • A prophylactic removal of colon (called prophylactic colectomy) can help decrease the chances of developing colon cancer
  • Drugs may be prescribed that can help decrease the number and size of the polyps.
  • Colon cancer can be treated through a combination of surgery, chemotherapy, and radiation therapy depending on the individual circumstances
  • The desmoid tumors can be surgically removed

How can Familial Adenomatous Polyposis Syndrome be Prevented?

Since Familial Adenomatous Polyposis Syndrome is a genetic disorder, there is no definitive prevention.

  • Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in better understanding the risks during pregnancy
  • If there is a family history of the condition, then genetic counseling may help couples assess risks while planning for a child
  • Active research is exploring treatment and prevention options for inherited and acquired genetic disorders

What is the Prognosis of Familial Adenomatous Polyposis Syndrome (Outcomes/Resolutions)

  • The prognosis of Familial Adenomatous Polyposis Syndrome depends on how early a diagnosis and medical intervention is performed
  • With no medical intervention, the median life expectancy of an individual diagnosed with Familial Adenomatous Polyposis Syndrome is 42 years
  • Prophylactic colectomy can increase the life expectancy

Additional and Relevant Useful Information for Familial Adenomatous Polyposis Syndrome:

Check out DoveMed’s digestive center for more medical information associated with the digestive system.

http://www.dovemed.com/healthy-living/digestive-center/

What are some Useful Resources for Additional Information?


References and Information Sources used for the Article:


Helpful Peer-Reviewed Medical Articles:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Sept. 8, 2015
Last updated: Sept. 11, 2018