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Familial adenomatous polyposis, also referred to as Gardner syndrome, is best described as an inherited colorectal cancer syndrome that is inherited. Roughly 1 percent of all colorectal cancers are associated with this syndrome. The syndrome runs in families and patients with this condition develop hundreds, or sometimes even thousands, or colon polyps. The development of these polyps usually begins during the teen years and all patients with this syndrome will develop colorectal cancer by about 40 years of age.
It is estimated that 87 percent of patients develop colon cancer by age 45. To prevent this cancer, patients with this syndrome must have their colon removed, and in some cases, their rectum. Other organs may also develop growths because the abnormal gene responsible for causing this syndrome is present is all cells within the body.
It is estimated that approximately one in 7,000 to one in 22,000 people are affected by this syndrome. Understanding the genetics of familial adenomatous polyposis will allow patients to better understand this syndrome and how and why it affects them.
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The genetics of familial adenomatous polyposis state that a APC gene mutation are responsible for causing this syndrome. The polyps develop due to the mutation causing cell overgrowth. Autosomal recessive familial adenomatous polyposis is caused by a MUTYH gene mutation. In addition to autosomal recessive, other possible inheritance patterns include autosomal dominant.
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Not all symptoms of this syndrome are related to cancer. Additional symptoms may include:
- Osteomas typically forming on the jaw
- An eye condition known as congenital hypertrophy of the retinal pigment epithelium
- Desmoid tumors
- Missing, unerupted, or extra teeth
- Fibromas, epidermoid cysts, and other benign skin changes
- Adrenal masses
The chance of developing certain other types of cancer is also higher for patients with this syndrome. These cancers include:
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Diagnosis will begin with determining whether or not the patient has a family history of this syndrome. If a family history is present and/or the symptoms fit, genetic testing will most likely be performed. Genetic testing is performed via blood testing. The patient's symptoms are then reexamined. Lastly, the patient's doctor will often examine the colon either using a barium enema or a scope.
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Most patients will have surgery to remove the polyps, but since there are hundreds of them, continuing to remove them individually is not effective. The types of surgery that may be performed include:
- Total colectomy and ileorectal anastamosis
- Proctocolectomy and ileostomy
- Colectomy with ileoanal pouch
Certain medications may also be prescribed to help prevent polyps from developing elsewhere in the body. Commonly prescribed medications include a non-steroidal anti-inflammatory drug referred to as sulindac and a COX-2 inhibitor known as celecoxib.
Monitoring the condition through regular check-ups and colon checks are also necessary.
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Cleveland Clinic. (2006). Familial Adenomatous Polyposis. Retrieved on September 16, 2010 from the Cleveland Clinic: http://www.clevelandclinic.org/registries/inherited/fap.htm
Genetics Home Reference. (2008). Familial Adenomatous Polyposis. Retrieved on September 16, 2010 from Genetics Home Reference: http://ghr.nlm.nih.gov/condition/familial-adenomatous-polyposis