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Colorectal Cancer: The Inherited Risk
photo of a calendar with a colonoscopy appointment on it

If you have colorectal cancer in your family, getting a colonoscopy done at the recommended ages is the key to an early diagnosis and getting proper treatment.

5 to 10 percent of all colorectal cancer cases are triggered by a heritable mutation (genetic alteration that can be passed on from a parent to the child). There are two major subtypes of hereditary colon cancer:

• Familial adenomatous polyposis (FAP)
• Lynch syndrome, commonly referred to as hereditary nonpolyposis colorectal cancer (HNPCC)

Besides, some rare conditions such as attenuated familial adenomatous polyposis (AFAP) and MUTYH-associated polyposis have been linked to an inherited risk of colorectal cancer. Also, there are other additional and unusual hereditary colorectal cancer causes that your physician will discuss with you if your family or personal history indicates that these symptoms might be present.

Some families have a strong history of colorectal cancer though no known mutations have been detected. Scientists don’t understand whether the susceptibility of these families to disease occurs randomly, or due to hereditary mutations that are yet to be identified.

Types of Hereditary Colorectal Cancer

The following are the different types of hereditary colon cancer.

1. Lynch Syndrome

Lynch Syndrome, also known as HNPCC, accounts for 2-3 percent of all diagnosed cases of colorectal cancer. Patients with this condition have an 80 percent risk of developing colorectal cancer as well as certain other types of cancer including tumors of the urinary tract, small intestines, pancreas, stomach, biliary system, ovary, and uterus.

Families with Lynch syndrome usually have:

• Three or more related members of the family diagnosed with colon cancer
• Affected members of the family in two or more generations
• At least one family member diagnosed with colorectal cancer before the age of 50

The mutations causing Lynch syndrome occur in the genes that take part in the DNA mismatch repair (a process that helps a cell to correct errors in the genetic code). These errors may arise randomly during cell division, or when the DNA is damaged. These mutations may trigger the accumulation of DNA errors in the cells, causing an increased risk of cancer.

2. Familial Adenomatous Polyposis

Familial adenomatous polyposis is rare, and it contributes to less than one percent of colorectal cancer. It is characterized by polyposis (the production of thousands of polyps in the colon) usually at a young age. Most often, untreated FAP causes the development of colorectal cancer at around the age of 40. In some cases, FAP can cause the development of stomach cancer or polyps in the upper gastrointestinal tract. Individuals diagnosed with FAP are strongly advised to seek medical help at specialized treatment centers such as GI North. A mutation in a gene called APC is responsible for FAP. People with the APC mutation have a 50 percent risk of passing this mutation on to a child.

3. Attenuated Familial Adenomatous Polyposis

Attenuated adenomatous polyposis (AFAP) is a milder form of FAP. People suffering from AFAP develop fewer polyps, usually between 30 and 100. If left untreated, AFAP can cause colorectal cancer by the time the individual reaches the age of 55. It can also cause stomach cancer or polyps in the upper gastrointestinal tract.

4. MUTYH-Associated Polyps

Researchers have discovered that mutations in a gene known as MUTYH may cause polyps that resemble those seen in AFAP. This condition is referred to as MUTYH-associated polyposis (MAP). It can be passed on from a parent to a child in an autosomal recessive manner. That is, a person needs to inherit two mutated genes —one from each parent— to produce cancer.

Genetic Testing for Colon Cancer

Several genetic tests can determine whether an individual has a genetic mutation that predisposes him or her to colon cancer. They include tests for MUTYH, MLH1, PMS2, MSH2, APC, and MSH6.

If you have a family history of colon cancer, you are highly encouraged to speak with a colonoscopy expert at GI North. Dr. Quijano and Dr. Cofrancesco serve the residents of Cumming, GA, as well as the surrounding areas of Canton, Roswell, Suwanee, Johns Creek, Dawsonville, and Alpharetta. Dr. Quijano also speaks fluent Spanish, and this is of great benefit to all Spanish-speaking people visiting GI North. Give GI North a call today at (404) 446-0600 for more information or to make an appointment.

© 2015 GI North Gastroenterology Services. All rights reserved.

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