Lynch syndrome Dr Trisha Macnair Symptoms include a change in bowel habit.

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What is Lynch syndrome? Symptoms

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Lynch syndrome, or hereditary non-polyposis colorectal cancer (HNPCC), is an inherited genetic mutation that causes of cancer of the bowel.

The genes affected are known as repair genes, which means they normally detect and repair damage in DNA. However, when they develop mutations this allows faulty DNA to persist, hence increasing the risk of cancer.

The main risk is bowel cancer – 90 per cent of men with the faulty gene and 70 per cent of women will have developed bowel cancer by the time they reach 70. But there is also an increased risk of other cancers too, such as cancer of the stomach, ovary, endometrium (the lining of the womb), pancreas, bile duct and urinary tract.

In people with HNPCC, bowel cancer typically develops at a younger age than non-hereditary bowel cancer - around the ages of 40 to 50 rather than 60-plus. However most bowel cancers occur in older people, and are not due to HNPCC.

So although HNPCC is one of the main causes when bowel cancer occurs in younger people, it's generally fairly rare, accounting for only 2-5 per cent of bowel cancers overall.

Symptoms include a change in bowel habit (needing to visit the toilet more frequently, with diarrhoea or constipation), the passage of blood with faeces, weight loss, change in appetite, abdominal pain and even an abdominal mass.

Once tumours develop, they are treated in the same way as a non-inherited bowel cancer. More than one tumour may be found in the colon.

Treatment will depend on where the tumour is and how far it has spread. In most cases, especially if the cancer is not advanced, surgery will be offered to remove the cancer, and then possibly chemotherapy (drug treatments), biological therapies (such as antibodies against substances known as growth factors) and occasionally radiotherapy.

Four genes have been identified as causing the majority of cases of HNPCC: hMLH1, hMSH2, hPMS1 and hPMS2. Blood tests can be used to detect them, although rarer mutations may be missed. It’s not possible to screen the whole population for these genes but once HNPCC has been diagnosed within a family, other family members may be screened for the specific gene mutation that has been discovered.

Those known to carry an HNPCC gene, or others in the family, should be vigilant for symptoms and can be screened for tumours with regular colonoscopy, gastroscopy and hysteroscopy usually every two years or so.

Antenatal screening of pregnant women within families affected by NHPCC (to check whether a baby within the womb carries the faulty gene) isn't usually offered.

Bowel Cancer UK
Tel: 0800 840 3540
Website: www.bowelcanceruk.org.uk

Beating Bowel Cancer
Tel: 08450 719300
Website: www.bowelcancer.org

Cancerbackup
Helpline: 0808 800 1234
Website: www.cancerbackup.org.uk

This article was last medically reviewed by Dr Trisha Macnair in March 2009.