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Understanding Lynch Syndrome: Causes, Risks, Diagnosis, and Treatment

Oghenefejiro Okifo | MD

Medically reviewed by Oghenefejiro Okifo | MD, Harvard Medical School | Henry Ford Hospital - Detroit, MI on November 4th, 2023.

Key Takeaways

  • Mutations in MLH1, MSH2, MSH6, PMS2, and EPCAM genes cause defective DNA mismatch repair, leading to 40-80% colorectal cancer risk by age 70 compared to 5% in the general population.

  • Affected individuals develop cancers 20-30 years earlier than average—colorectal cancer typically emerges in the 30s-40s, while endometrial cancer affects 40-60% of women with the condition.

  • Each child of an affected parent has a 50% chance of inheriting the mutation, making genetic counseling and cascade testing of family members crucial for early detection.

  • Colonoscopy screening begins at age 20-25 (or 2-5 years before the youngest family cancer diagnosis) and continues every 1-2 years, catching 90% of cancers when still curable.

  • Prophylactic hysterectomy and oophorectomy after childbearing can reduce endometrial cancer risk by 95% and ovarian cancer risk by 85% in high-risk women.

Lynch syndrome is a genetic condition that increases a person's risk of developing certain types of cancer, particularly colorectal cancer. It is caused by inherited changes in specific genes that normally help repair DNA damage in cells. When these genes are not functioning properly, cells can accumulate errors and potentially become cancerous.

People with Lynch syndrome have a 40% to 80% chance of developing colorectal cancer by the age of 70. They are also at an increased risk for other cancers, such as uterine, ovarian, and stomach cancer. These cancers often occur at younger ages compared to the general population, typically in a person's 30s and 40s.

Understanding Lynch Syndrome: Causes, Risks, Diagnosis, and Treatment

Causes of Lynch Syndrome

Lynch syndrome is caused by inherited changes in one of five genes responsible for repairing DNA errors during cell growth and division. When a person has Lynch syndrome, their cells are unable to fix these mistakes, leading to the accumulation of flawed cells that can eventually develop into cancer.

If one parent has Lynch syndrome, their children have a 50% chance of inheriting the condition.

Signs and Symptoms of Lynch Syndrome

Some signs that may indicate a risk of Lynch syndrome include:

  • Developing colorectal cancer before the age of 50

  • Having family members who were diagnosed with colorectal cancer at a young age

  • Women in the family with a history of endometrial or uterine cancer

  • Family members with a history of kidney, liver, small intestine, stomach, or sebaceous gland cancer

Diagnosing Lynch Syndrome

If a person or their family member is diagnosed with cancer, doctors can perform tests on a small sample of the tumor to look for signs of Lynch syndrome. These tests include:

  • Immunohistochemistry (IHC) tests: These tests use dye to mark proteins in the tumor sample. The absence of certain proteins may indicate Lynch syndrome.

  • Microsatellite instability (MSI) tests: These tests examine the DNA in the tumor tissue, looking for errors in genes that suggest Lynch syndrome.

Genetic testing using a blood sample can also be done to confirm a Lynch syndrome diagnosis or to determine if a person is at risk of developing the condition. Consulting with a genetic counselor can help individuals understand their risks, options, and the implications of genetic testing.

Treatment Options for Lynch Syndrome

Regular screenings are crucial for individuals with Lynch syndrome to detect cancers at their earliest stages when they are most treatable. Colon cancer, for example, has a 90% cure rate when caught early. People at risk should begin screenings much earlier than the general population.

Screening guidelines for Lynch syndrome may include:

  • Colonoscopies every 1 to 2 years, starting at age 20 to 25

  • Endoscopies every 3 to 5 years, beginning in the early to mid-30s

  • Annual pelvic exams, uterine biopsies, or transvaginal ultrasounds for women, starting around age 30

In some cases, individuals with Lynch syndrome may choose to have preventive surgery, such as removing the colon or, for women who do not plan to have children, removing the uterus and ovaries.

Maintaining a healthy lifestyle, including a diet rich in vegetables, fruits, and whole grains, regular exercise, maintaining a healthy weight, and limiting alcohol consumption, may also help reduce the risk of Lynch-related cancers.

For more information on Lynch syndrome, visit the following reputable sources:

The Bottom Line

Early genetic testing and aggressive screening starting in the 20s can prevent most Lynch syndrome cancers through early detection or prophylactic surgery. The key is identifying at-risk families through genetic counseling when multiple relatives develop colorectal, endometrial, or other associated cancers at young ages. If you have a strong family history of early-onset cancers, Doctronic can help connect you with genetic testing and specialized screening protocols.

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