Lynch syndrome is an inherited condition that increases your risk of colon cancer and 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, but Lynch syndrome is the most common. Doctors estimate that about 3 out of every 100 colon cancers are caused by Lynch syndrome.

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


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 it up with your doctor. Discuss getting 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 and help you understand whether genetic testing is appropriate for you.


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 the child is a son or daughter.

How gene mutations cause cancer

The genes inherited in Lynch syndrome are normally responsible for correcting mistakes 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 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 lead to the cells becoming cancerous.


Beyond complications for your health, a genetic disorder such as Lynch syndrome may be cause for 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 worry that being diagnosed with Lynch syndrome will make it difficult to change jobs or health insurance providers in the future. Federal laws protect Americans from discrimination. A genetic counselor can explain legal protections.
  • 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.
  • Your extended family. A Lynch syndrome diagnosis has implications for your entire family. You may worry about the best way to tell family members that you're having genetic testing. A genetic counselor can guide you through this process.


Frequent cancer screening, preventive surgery and aspirin are options for reducing the risk of cancer in people with Lynch syndrome.

Taking care of yourself through diet, exercise and other lifestyle changes can help improve your overall health.

Take control of your health by trying to:

  • Eat a healthy diet full of fruits and vegetables. Choose a variety of fruits and vegetables for your diet. Also, select whole-grain products when possible.
  • Exercise regularly. Aim for at least 30 minutes of exercise most days of the week. If you haven't been active, talk to your doctor before you begin an exercise program. Try gentle exercises like walking or biking to get started.
  • Maintain a healthy weight. A healthy diet and regular exercise can help you maintain a healthy weight. If you need to lose weight, talk with your doctor about your options. Eating fewer calories and increasing the amount of exercise you do can help you lose weight. Aim to lose 1 or 2 pounds a week.
  • Stop smoking. Smoking increases your risk of several types of cancer and other health conditions. Some evidence indicates smoking may increase the risk of colon cancer in people with Lynch syndrome.

    If you smoke, stop. Your doctor can recommend strategies to help you quit. You have many options, such as nicotine replacement products, medications and support groups. If you don't smoke, don't start.

Lynch syndrome care at Mayo Clinic

March 13, 2015
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