What is Lynch syndrome?

Lynch syndrome (LS) is a genetic condition that can run in families and increases a person’s risk of developing different types of cancer. It used to be called hereditary non-polyposis colon cancer (HNPCC). People with LS have up to an 80% lifetime risk of colorectal cancer. LS is also associated with an increased risk of womb cancer, ovarian cancer, and to a lesser extent stomach, pancreatic, small bowel, skin, brain, kidney and bladder cancer.

How does Lynch syndrome occur?

LS occurs due to a variant or mutation in a gene. We have genes called DNA mismatch repair genes which correct errors made in cell division. These genes can therefore stop cells from multiplying out of control and can protect us from developing cancer. However, for people with LS one of these genes doesn’t work properly, which means they have less protection against cancer.

People with LS have a variant in the MLH1, MSH2, MSH6, PMS2 or EPCAM gene.

How is Lynch syndrome inherited?

Genes are passed from parents to children. We have two copies of each gene, one inherited from our mother and one from our father. If one parent has LS, or one gene variant, they may pass this down to their children, or they may pass on their “normal” gene. This means that if you have Lynch syndrome, there is a 50% chance your children will inherit it.

In very rare cases, if both parents have Lynch syndrome a child could inherit both gene variants and have constitutional mismatch repair deficiency (CMMRD). This comes with its own cancer risks but is an ultra-rare condition – it is estimated that one in a million people in the world have CMMRD.

How is Lynch syndrome diagnosed?

LS is diagnosed through genetic testing. If you have had cancer, this may first be done using a sample of your cancer cells. A blood test can then be carried out to check for the gene variants that cause LS, and potentially affected family members can also have a blood test to confirm if they have LS.

Patterns of cancer in a family may suggest the presence of LS. This might be several close relatives over several generations developing cancer linked to LS, for example parents, siblings, children, aunts, uncles and grandparents. It could also be someone developing bowel cancer before the age of 50, developing another LS cancer at a young age, or developing two different types of cancer linked to LS. Speak to your GP if you are concerned.

How is Lynch syndrome treated?

Though LS itself cannot be treated, regular screening is the best approach for finding cancer at an early stage in those with increased risk. This includes a regular colonoscopy to screen for bowel cancer by looking inside the large bowel to find and remove polyps.

Studies have shown that taking aspirin regularly can help prevent bowel cancer in people with LS. The dosage prescribed may vary between patients. Always speak to your doctor before making any changes to the medications you take.

People with LS may also undergo risk-reducing surgery, such as the removal of the womb and ovaries to reduce the risk of cancer. If a person with LS develops bowel cancer, surgery may be offered to remove healthy parts of the bowel as well as the area affected by the tumour, to reduce the risk of the cancer returning.