What genetic syndromes are associated with increased colorectal cancer risk?

Familial adenomatous polyposis (FAP) and Lynch syndrome are both genetic syndromes that are directly associated with a significant increase in the risk of developing colorectal cancer.

Familial adenomatous polyposis is characterized by the formation of hundreds to thousands of polyps in the colon and rectum, which begin to appear in adolescence or early adulthood. If not managed, individuals with FAP will almost inevitably develop colorectal cancer, often before they reach the age of 40. The genetic basis for FAP is usually a mutation in the APC gene, which is a tumor suppressor gene.

Lynch syndrome, also known as hereditary non-polyposis colorectal cancer (HNPCC), is caused by mutations in mismatch repair genes that lead to microsatellite instability. Individuals with Lynch syndrome have a higher risk not only for colorectal cancer but also for other types of cancer, including endometrial, stomach, and ovarian cancers. The risk of developing colorectal cancer in individuals with Lynch syndrome can be as high as 80% by age 70.

In contrast, while BRCA1 and BRCA2 mutations are primarily associated with breast and ovarian cancers, they do not have the same direct connection to colorectal cancer risk. Li-Fraumeni syndrome