Lynch syndrome

The genes that are responsible for causing Lynch syndrome are involved in the DNA mismatch repair system. This system is very important for cells to repair errors that inevitably occur in DNA over a person's lifetime. Repairing errors in DNA is important to maintaining the integrity of DNA, as errors that occur in certain places in the DNA can lead to the development of cancer.

All of our genes are present in pairs. One copy in each pair is from our mother, and the other copy is from our father. Inheriting a single mutation in one copy of any of the Lynch syndrome genes causes Lynch syndrome. This is called dominant inheritance.

A person with a Lynch syndrome gene mutation has a 50 percent chance of passing the gene mutation to a child. Men and women are equally at risk of inheriting a gene mutation causing Lynch syndrome. If a child does not inherit the gene mutation, the mutations cannot be passed along to the next generation by this child as these gene mutations do not skip a generation.

Families with Lynch syndrome may have several relatives in multiple generations affected by a Lynch syndrome cancer. The cancers seen in Lynch syndrome also may arise at earlier than average ages.

In general, genetic testing for Lynch syndrome may be appropriate for a person with the following:

• Colon cancer or uterine cancer before age 50
• A history of more than one Lynch syndrome-associated cancer (i.e., colon cancer plus uterine cancer)
• Multiple family members with Lynch syndrome-associated cancers
• A family member with a known diagnosis of Lynch syndrome
• A tumor with features suggestive of Lynch syndrome (i.e., tumor testing by a Pathologist may show an abnormal result on mismatch repair immunohistochemistry, also known as an MMR-IHC test)

Given the multiple increased cancer risks in Lynch syndrome, it is important that individuals with Lynch syndrome be managed by a multi-disciplinary team of providers with expertise in Lynch syndrome.