Overview

Lynch syndrome is an inherited condition that increases your risk of colon cancer, endometrial cancer and several other cancers. Lynch syndrome has historically been known as hereditary nonpolyposis colorectal cancer (HNPCC).

A number of inherited syndromes can increase your risk of colon cancer or endometrial cancer, but Lynch syndrome is the most common. Doctors estimate that around 3 out of every 100 colon cancers or endometrial cancers are caused by Lynch syndrome.

Families that have Lynch syndrome usually have more instances of colon cancer or endometrial cancer than would typically be expected. Lynch syndrome also causes cancers to occur at an earlier age than they might in the general population.

Symptoms

People with Lynch syndrome may experience:

  • Colon cancer that occurs at a younger age, especially before age 50
  • A family history of colon cancer that occurs at a young age
  • A family history of cancer that affects the uterus (endometrial cancer)
  • A family history of other related cancers, including ovarian cancer, kidney cancer, stomach cancer, small intestine cancer, liver cancer, sweat gland cancer (sebaceous carcinoma) and other cancers

When to see a doctor

If you have concerns about your family history of colon or endometrial cancer, bring them up with your doctor. Together, you and your doctor may consider having a genetic evaluation of your family history and your cancer risk.

If a family member has been diagnosed with Lynch syndrome, tell your doctor. Ask to be referred to a genetic counselor. Genetic counselors are trained in genetics and counseling. They can help you understand Lynch syndrome, what causes it and what type of care is recommended for people who have Lynch syndrome. A genetic counselor can also help you sort through all the information about the disease and help you understand whether genetic testing is appropriate for you.

Causes

Lynch syndrome runs in families in an autosomal dominant inheritance pattern. This means that if one parent carries a gene mutation for Lynch syndrome, there's a 50 percent chance that mutation will be passed on to each child. The risk of Lynch syndrome is the same whether the gene mutation carrier is the mother or father or whether the child is a son or daughter.

How gene mutations cause cancer

The genes affected in Lynch syndrome are responsible for correcting changes in the genetic code (mismatch repair genes).

Your genes contain DNA, which carries instructions for every chemical process in your body. As your cells grow and divide, they make copies of their DNA and it's not uncommon for some minor mistakes to occur.

Normal cells have mechanisms to recognize mistakes and repair them. But the cells of people who inherit one of the abnormal genes associated with Lynch syndrome lack the ability to repair these minor mistakes. An accumulation of these mistakes leads to increasing genetic damage within cells and eventually can cause the cells to become cancerous.

Complications

Beyond causing complications for your health, a genetic disorder such as Lynch syndrome may raise other concerns. A genetic counselor is trained to help you navigate the areas of your life that may be affected by your diagnosis, such as:

  • Your privacy. The results of your genetic test will be listed in your medical record, which may be accessed by insurance companies and employers. You may have questions about whether being diagnosed with Lynch syndrome will make it difficult to change jobs or health insurance providers in the future. A genetic counselor can explain the laws that may protect you.
  • Your children. If you have Lynch syndrome, your children have a risk of inheriting your genetic mutations. If one parent carries a genetic mutation for Lynch syndrome, each child has a 50 percent chance of inheriting that mutation. A genetic counselor can help you develop a plan for discussing this with your children, including how and when to tell them and when they should consider testing.
  • Your extended family. A Lynch syndrome diagnosis has implications for your entire family, as many other blood relatives may have a chance of having Lynch syndrome. A genetic counselor can assist you in finding the best way to tell family members that you're having genetic testing and what that the results mean.

Lynch syndrome care at Mayo Clinic

May 17, 2018
References
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  2. AskMayoExpert. Lynch syndrome. Rochester, Minn.: Mayo Foundation for Medical Education and Research; 2017.
  3. Genetic/familial high-risk assessment: Colorectal. Fort Washington, Pa.: National Comprehensive Cancer Network. http://www.nccn.org/professionals/physician_gls/f_guidelines.asp. Accessed March 3, 2018.
  4. Making sense of your genes: A guide to genetic counseling. Genetic Alliance. http://www.geneticalliance.org/publications/guidetogeneticcounseling. Accessed March 29, 2018.
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  7. Thibodeau SN, et al. Microsatellite instability in cancer of the proximal colon. Science. 1993;260:816.
  8. Lu KH, et al. Endometrial and ovarian cancer screening and prevention in women with Lynch syndrome (hereditary nonpolyposis colorectal cancer). https://www.uptodate.com/contents/search. Accessed April 9, 2018.