Lynch Syndrome Case 1

Lynch syndrome, also known as hereditary nonpolyposis colorectal cancer (HNPCC), is an autosomal dominant genetic disorder that significantly increases the risk of developing various types of cancer, most notably colorectal and endometrial cancers. It is caused by germline mutations in mismatch repair (MMR) genes, primarily MLH1, MSH2, MSH6, PMS2, and EPCAM. These genes are responsible for correcting DNA replication errors, and their malfunction leads to microsatellite instability (MSI) and accumulation of mutations, which promotes cancer development.

Key Characteristics:

• Inheritance: Autosomal dominant, meaning a single mutated copy of the gene can increase cancer risk.
• Cancer Risk: High lifetime risk of colorectal cancer (up to 80%) and endometrial cancer (up to 60%). Increased risk for other cancers, including ovarian, stomach, small intestine, hepatobiliary tract, upper urinary tract, brain, and skin.
• Diagnosis: Based on family history, genetic testing for MMR gene mutations, and tumor testing for MSI or loss of MMR protein expression by immunohistochemistry (IHC).
• Surveillance and Management: Regular screening starting at an early age, including colonoscopy every 1-2 years beginning at age 20-25, and considering prophylactic surgeries. Endometrial and ovarian cancer screening may also be recommended.

Lynch syndrome's early identification and proactive management significantly improve patient outcomes by allowing for timely cancer detection and prevention.