Hereditary non-polyposis colorectal cancer (HNPCC) Dr Trisha Macnair In Britain one in fifty of people with bowel cancer will have HNPCC, also known as Lynch syndrome.

In this article

What is it? Symptoms

Causes and risk factors Treatment and recovery

HNPCC is an inherited genetic mutation that causes of bowel cancer.

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 to 70.

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.

The genes affected are known as repair genes, which means they normally detect and repair damage in DNA that occurs when DNA is copied during cell division. However, when the genetic mutations are present, mistakes in DNA persist. The faulty DNA accumulates leading to uncontrolled cell growth and hence a risk of cancer.

The genes associated with HNPCC can sometimes cause other cancers, such as stomach, small intestine, liver, gall-bladder, ovary, endometrium (the lining of the womb), kidney, brain, skin and prostate gland.

Once tumours develop, they are treated in the same way as a non-inherited bowel cancer. However, someone with the abnormal genes can be screened for tumours.

However, someone known to have an abnormal HNPCC gene (or others in the family) can be screened for tumours with regular colonoscopy, gastroscopy and hysteroscopy, so problems may be caught much earlier when treatment is more likely to be effective.

Seven genes have been identified as causing the majority of cases of HNPCC: MSH2, MLH1, PMS1, PMS2, MSH6, TGFBR2 and MLH3. Blood tests may be used to detect them. These genes for HNPCC are inherited in an autosomal dominant pattern, which means that a person has a 50% chance of passing the abnormal gene on to each of their children. However this doesn’t mean a 50% chance of cancer in the child as not all those who inherit the genetic mutation will go on to develop cancer.

Antenatal screening is not usually offered.

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