Inherited Conditions Associated with Colorectal Cancer

In some families, a rare genetic mutation makes it more likely that a family member will develop colorectal cancer. These inherited conditions include:

• Familial Adenomatous Polyposis (FAP)
  A person with familial adenomatous polyposis (FAP) develops hundreds or even thousands of polyps in the colon and rectum. FAP usually appears during the teenage years. In the vast majority of cases, cancer develops in one or more of these polyps, usually between the ages of 30 and 50, but sometimes at a younger age. This condition occurs because a gene that normally prevents tumour growth is absent or damaged.

• Hereditary Nonpolyposis Colon Cancer (HNPCC)
  Hereditary nonpolyposis colon cancer (HNPCC, also known as Lynch Syndrome) is the most common type of genetic colorectal cancer. People with this condition tend to develop cancer at a young age, but do not have as many polyps as those with FAP (described above). HNPCC is the result of a genetic defect, which prevents the body from repairing genetic errors in new cells. HNPCC increases a person’s risk of developing other cancers as well.

• Peutz-Jeghers Syndrome (JPS)
  Peutz-Jeghers Syndrome (JPS) causes polyps on a person’s small intestine and colon, as well as small dark freckles on their cheeks, lips, fingertips and toes. These blue, brown or black freckles often appear during infancy or childhood, providing an early indication that a child has the disease.  

• Juvenile Polyposis
  People with juvenile polyposis develop polyps throughout their gastrointestinal tract, especially in the large intestine and bowel, in early childhood. These polyps often become cancerous. The disease is frequently misdiagnosed because of its similarity to FAP.

Tests have been developed to detect the genetic mutations that cause syndromes such as FAP and HNPCC. In families where these mutations have been identified, testing can help determine which members of the families have inherited the condition. Genetic testing is usually available only if a member of your family has colorectal cancer and has been found to carry one of these genetic mutations. A genetic counselor can discuss the benefits and risks of genetic testing with you.

People with these conditions should have a colonoscopy at an early age, to be screened for colorectal cancer.

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