Hereditary Nonpolyposis Colorectal Cancer (Lynch Syndrome)

Hereditary Nonpolyposis Colorectal Cancer (Lynch Syndrome) is a genetic condition that increases the risk of developing colorectal cancer and other types of cancer, often at a younger age than usual. It primarily affects the colon and rectum, which are parts of the digestive system responsible for processing waste. People with this condition have inherited changes in certain genes that normally help repair DNA damage, leading to a higher chance of cancer developing. Besides colorectal cancer, it also raises the risk for cancers of the endometrium, stomach, ovaries, and other organs. Early detection and monitoring are important because cancers linked to this syndrome can grow quickly but may be caught early with regular screening. Understanding this condition helps explain why some families have multiple members with these cancers.

Hereditary Nonpolyposis Colorectal Cancer (Lynch Syndrome) is an autosomal dominant inherited cancer syndrome caused by germline mutations in DNA mismatch repair genes such as MLH1, MSH2, MSH6, and PMS2. These mutations lead to microsatellite instability (MSI) and accumulation of DNA replication errors, resulting in increased risk of early-onset colorectal cancer and various extracolonic malignancies, including endometrial, gastric, and ovarian cancers. The syndrome is characterized by the absence of numerous polyps, distinguishing it from familial adenomatous polyposis. Clinically, affected individuals often present with colorectal cancer before age 50 and have a family history consistent with autosomal dominant inheritance. Identification of Lynch syndrome is critical due to its implications for cancer surveillance and prevention in patients and their relatives.