Information for people and families with Lynch Syndrome

If you or some of your family members have Lynch Syndrome caused by a faulty gene, this is some information to help you understand what it means. It is always advisable to have a discussion with your doctor or a genetic counselor.

What is Lynch Syndrome?
Lynch syndrome is an inherited condition which means that you will have an increased risk of developing bowel cancer, cancer of the lining of the womb (endometrial cancer) and other cancers. Lynch syndrome is sometimes known as HNPCC (hereditary nonpolyposis colorectal cancer).

What causes Lynch Syndrome?
Faulty genes (mutation) can cause  Lynch Syndrome. There are four Lynch syndrome genes which are called MLH1, MSH2, MSH6 and PMS2. These genes are known as mismatch repair genes as they normally repair mistakes in the cell’s DNA to protect against cancer, primarily in the lining of the large bowel and uterus (endometrium). If you have a faulty Lynch gene, cancer may develop froman accumulation of these mistakes.

How is Lynch Syndrome Inherited?
Lynch Syndrome is a condition that is passed from parent to child. Occasionally it may occur “out of the blue‟ with no family history. Each child of a parent with Lynch Syndrome has a 50:50 chance of inheriting the genetic spelling mistake and each of those person’s children then has the 50:50 chance of inheriting it. This is called anautosomal dominant inheritance pattern.

What are the Risks of Cancer in Lynch Syndrome?
If you are a male with Lynch syndrome you have about a 38% risk of developing cancer of the large bowel and about a 7% risk of developing stomach cancer over your lifetime.

If you are woman with Lynch syndrome you have about a 31% risk of developing bowel cancer, 33% risk of developing cancer of the lining of the uterus (endometrial cancer), a 7% risk of developing stomach cancer and 9% risk of ovarian cancer.

Risks do vary depending on which gene is involved. The risk of developing both bowel and other cancers varies between families. This mostly relates to the type of genetic mutation in each family. Occasionally other cancers may develop, although these are not common.

Not everybody with Lynch syndrome develops cancer.

Genetic Testing
Once a faulty gene has been identified in a family member with cancer, genetic testing (predictive testing) via a blood/saliva test is available to other adult family members to see if they have also inherited the faulty gene. There are a number of significant emotional, psychological, family and practical issues associated with genetictesting which you and your family members should discuss with a genetics counselor.

How is Lynch Syndrome Managed?
It is recommended that anyone with Lynch syndrome in their family should seek management advice from a genetic service or a family cancer clinic.

Bowel Screening

  • Regular bowel screening tests by colonoscopy from the age of 25 (younger in some families) is important for individuals with Lynch syndrome and their at-risk family members. Colonoscopy detects and removes precancerous growths (polyps) in the bowel to prevent them from developing into cancer.

Gynaecological Management

  • Women with Lynch syndrome should discuss their gynaecological management with their doctors.

Prophylactic total hysterectomy (risk reducing surgery) should be offered to women whose childbearing is complete or to omen undergoing abdominal surgery for other conditions, especially when there is endometrial cancer in the family. This recommendation is based on the high rate of endometrial cancer in mutation positive individuals (43%), and the lack of efficacy of screening.

Removal of ovaries and fallopian tubes should also be performed because of the high incidence of ovarian cancer as well (9%) and the frequent coexistence of endometrial and ovarian cancer.

If you decide not to have genetic testing but have a strong family history the risk management strategy above is still recommended.

After genetic testing:

If you do carry a faulty Lynch syndrome gene:

  • You are at increased risk of developing cancers associated with the family gene fault
  • It can be passed from one generation to the next
  • Each of your children has a 50% (or 1 in 2) chance of inheriting it

If you do not have a faulty gene:

  • You are not at increased risk of cancer(s) known to be associated with the family gene fault, and have the same risk as the general population (unless there are other factors which may increase
    your risk)
  • You cannot pass it on to your children
  • Your siblings may still carry a faulty gene
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