Overview

Lynch syndrome is a condition that increases the risk of many kinds of cancer. This condition is passed from parents to children.

Families that have Lynch syndrome have more instances of cancer than expected. This might include colon cancer, endometrial cancer and other types of cancer. Lynch syndrome also causes cancers to happen at an earlier age.

People with Lynch syndrome may need careful testing to look for cancer when it's small. Treatment is more likely to be successful when the cancer is caught early. Some people with Lynch syndrome might consider treatments to prevent cancer.

Lynch syndrome used to be called hereditary nonpolyposis colorectal cancer (HNPCC). HNPCC is a term used to describe families with a strong history of colon cancer. Lynch syndrome is the term used when doctors find a gene that runs in the family and causes cancer.

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Symptoms

People with Lynch syndrome may experience:

  • Colon cancer before age 50
  • Cancer of the inside lining of the uterus (endometrial cancer) before age 50
  • A personal history of more than one type of cancer
  • A family history of cancer before age 50
  • A family history of other cancers caused by Lynch syndrome, including stomach cancer, ovarian cancer, pancreatic cancer, kidney cancer, bladder cancer, ureteral cancer, brain cancer, small intestine cancer, gallbladder cancer, bile duct cancer and skin cancer

When to see a doctor

If a family member has Lynch syndrome, tell your health care provider. Ask your provider to help set up an appointment with a professional trained in genetics, such as a genetic counselor. This person can help you understand Lynch syndrome, what causes it and whether genetic testing is right for you.

Causes

Lynch syndrome is caused by genes that are passed from parents to children.

Genes are pieces of DNA. DNA is like a set of instructions for every chemical process that happens in the body.

As cells grow and make new cells as part of their lifecycle, they make copies of their DNA. Sometimes the copies have errors. The body has a set of genes that hold the instructions for finding the errors and fixing them. Doctors call these genes mismatch repair genes.

People with Lynch syndrome have mismatch repair genes that don't work as expected. If an error happens in the DNA, it might not get fixed. This could cause cells that grow out of control and become cancer cells.

Lynch syndrome runs in families in an autosomal dominant inheritance pattern. This means that if one parent has genes that cause Lynch syndrome, there's a 50% chance that each child will have the genes that cause Lynch syndrome. Which parent carries the gene doesn't affect the risk.

Complications

Knowing that you have Lynch syndrome can raise concerns about your health. It may also raise some concerns about other parts of your life. These might include:

  • Your privacy. You may have questions about what could happen if others find out you have Lynch syndrome. For instance, you might be concerned that your job or insurance companies might find out. A genetics professional can explain the laws that may protect you.
  • Your children. If you have Lynch syndrome, your children have a risk of inheriting it from you. A genetics professional can help you come up with a plan for talking about this with your children. The plan might include how and when to tell them and when they should consider testing.
  • Your extended family. Having Lynch syndrome has implications for your entire family. Other blood relatives may have a chance of having Lynch syndrome. A genetics professional can help you come up with the best way to tell family members.

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July 15, 2022

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  2. Genetic/familial high-risk assessment: Colorectal. National Comprehensive Cancer Network. https://www.nccn.org/guidelines/guidelines-detail?category=2&id=1436. Accessed May 19, 2022.
  3. Biller LH, et al. Lynch syndrome-associated cancers beyond colorectal cancer. Gastrointestinal Endoscopy Clinics of North America. 2022; doi:10.1016/j.giec.2021.08.002.
  4. What to expect when meeting with a genetic counselor. Cancer.Net. https://www.cancer.net/navigating-cancer-care/cancer-basics/genetics/what-expect-when-meeting-genetic-counselor. Accessed May 27, 2022.
  5. DeJene Gemechu S, et al. Do the risks of Lynch syndrome-related cancer depend on the parent of origin of the mutation? Familial Cancer. 2020; doi:10.1007/s10689-020-00167-4.
  6. Genetics of colorectal cancer (PDQ) ¬– Health professional version. National Cancer Institute. https://www.cancer.gov/types/colorectal/hp/colorectal-genetics-pdq. Accessed May 27, 2022.
  7. Lynch HT, et al. Milestones of Lynch syndrome: 1895-2015. Nature Reviews Cancer. 2015; doi:10.1038/nrc3878.
  8. Thibodeau SN, et al. Microsatellite instability in cancer of the proximal colon. Science. 1993; http://www.jstor.org/stable/2881173. Accessed May 27, 2022.

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