Lynch syndrome is a genetic condition that increases a person's risk for certain cancers. It is the most common inherited cause of colorectal and endometrial cancers. People with Lynch syndrome have a defect in a gene that helps repair damaged DNA, which can lead to the development of cancerous cells. Many individuals with a Lynch mutation develop related cancers at very early ages, much younger than the general population. People with Lynch syndrome may be advised to undergo regular cancer screening tests starting at a younger age to detect cancer early, when it is most treatable.