Short answer · Medically reviewed summary · Last updated: 2026-05-08
Lynch Syndrome, also known as hereditary non-polyposis colorectal cancer (HNPCC), is a genetic condition that significantly increases the risk of developing colorectal and various other cancers at an earlier age than the general population. It is caused by inherited mutations in genes responsible for repairing DNA, which impairs the body's ability to fix errors that occur during cell division. What causes Lynch Syndrome? Lynch Syndrome is primarily caused by a germline mutation in one of the mismatch repair (MMR) genes: MLH1, MSH2, MSH6, or PMS2, or through a deletion in the EPCAM gene.
What is Lynch Syndrome
What is Lynch Syndrome? Plain-language, medically reviewed definition plus the lived reality told by patients.
Lynch Syndrome, also known as hereditary non-polyposis colorectal cancer (HNPCC), is a genetic condition that significantly increases the risk of developing colorectal and various other cancers at an earlier age than the general population. It is caused by inherited mutations in genes responsible for repairing DNA, which impairs the body's ability to fix errors that occur during cell division.
What causes Lynch Syndrome?
Lynch Syndrome is primarily caused by a germline mutation in one of the mismatch repair (MMR) genes: MLH1, MSH2, MSH6, or PMS2, or through a deletion in the EPCAM gene. Under normal conditions, these genes act as "spell-checkers" for DNA; when they are faulty, cells accumulate genetic errors rapidly, leading to uncontrolled growth and tumor formation. Lynch Syndrome is inherited in an autosomal dominant pattern, meaning a child of an affected parent has a 50% chance of inheriting the mutation.
Which body systems are affected by Lynch Syndrome?
While the digestive system is the most frequent site for malignancies, Lynch Syndrome can predispose individuals to cancers in several organ systems. The specific risks vary based on which gene is mutated:
- Colorectal: Significantly elevated lifetime risk (up to 80% depending on the specific gene).
- Endometrial: The second most common cancer site, particularly in women.
- Other systems: Increased risks for cancers of the stomach, ovaries, small bowel, urinary tract, hepatobiliary tract, and sebaceous skin tumors.
How common is Lynch Syndrome?
Lynch Syndrome is estimated to affect approximately 1 in 300 to 1 in 400 individuals in the general population, making it one of the most common hereditary cancer syndromes. It affects men and women equally, and because it is a genetic condition, it is present from birth, though cancer development typically occurs during adulthood, often between the ages of 30 and 50.
What differentiates Lynch Syndrome from other conditions?
Unlike Familial Adenomatous Polyposis (FAP), which is characterized by the presence of hundreds or thousands of polyps, Lynch Syndrome often involves the development of fewer polyps that progress to cancer much more rapidly. This "accelerated carcinogenesis" necessitates more frequent screening, such as colonoscopies every 1-2 years.
Next steps
- Consult with a genetic counselor to discuss family history and potential genetic testing.
- Speak with a gastroenterologist about establishing an intensive surveillance schedule.
- Connect with the 79 members of the Lynch Syndrome community at DiseaseMaps.org to share experiences and find support.
Medical disclaimer: This information is for educational purposes and should not replace professional medical advice, diagnosis, or treatment.
References
- NIH Genetic and Rare Diseases Information Center (GARD): Lynch Syndrome Overview.
- Orphanet: Hereditary non-polyposis colorectal cancer (ORPHA:144).
- OMIM (Online Mendelian Inheritance in Man): Entry #120435.
- National Cancer Institute (NCI): Genetics of Colorectal Cancer (PDQ®).
