What is Lynch syndrome?

Lynch syndrome, also known as HNPCC (hereditary non-polyposis colorectal cancer), is an inherited disorder that increases the risk of many types of cancer, particularly cancers of the colon (large intestine) and rectum, which are collectively referred to as colorectal cancer.

Patients with Lynch syndrome usually develop colorectal cancer before the age of 50. The condition is usually diagnosed and treated by obstetricians and gynaecologists. 

In addition to colorectal cancer, HNPCC has an associated risk with the development of other cancers of the gastrointestinal tract or reproductive system, such as stomach cancer, ovarian cancer, urinary tract cancer, endometrial cancer, intestinal cancer, and pancreatic cancer.

How is Lynch syndrome diagnosed?

In order to diagnose you with Lynch syndrome, the doctor will classify your situation by the Amsterdam clinical criteria and will have you do a genetic test for tumour markers focusing on molecular screening, in order to identify DNA mismatches.

You may be diagnosed with Lynch syndrome if you fulfil the following criteria:

• Developing colorectal cancer at a young age (typically younger than 50)
• Family history of colorectal cancer at a young age
• Family history of related cancers of the digestive or reproductive systems.

HNPCC is an autosomal dominant genetic condition. This means that if you have Lynch syndrome, there’s a 50 per centchance that your children will inherit this condition.

If you’re suffering from any symptoms of colorectal cancer, you should talk with your GP, especially if there’s a family history of one or more gastrointestinal tract cancers.

What causes Lynch syndrome?

Lynch syndrome is caused by inherited mutations that impair DNA mismatch repair. The MMR (mismatch repair) genes are responsible for recognizing and repairing errors that can arise during DNA replication and recombination.

In individuals with HNPCC, this process is impaired. This, in turn, can cause other genetic mutations, which lead to an increased risk of colorectal cancer.

How can it be prevented?

Being an inherited condition, Lynch syndrome can’t be prevented. However, if you are aware that you have Lynch syndrome, you can try to catch cancer early and treat it. First of all, you should check if anyone in your family has HNPCC.

If there is a family history of Lynch syndrome, everyone who is 20 or older should have a colonoscopy every year, even if they’re not showing any signs of cancer. Should the colonoscopy show that there are adenomatous colorectal polyps, these can be removed, so that they won’t evolve into a tumour.

Women 35 or older should take periodic gynaecological tests to avoid getting an endometrial cancer.

Men who have HNPCC have a higher risk of getting colorectal cancer, compared to women with the same condition. On the other hand, women who have HNPCC also have an elevated risk of getting endometrial cancer. There’s a further 10% chance that the syndrome will cause any other kind of neoplasm and the vast majority of individuals with Lynch syndrome will get some kind of cancers during their lifetime. It is therefore essential to go for periodic medical examinations if you have HNPCC.

How can Lynch syndrome be treated?

Lynch syndrome itself cannot be treated, but if cancer develops and is diagnosed early enough, it may be treatable:

• Surgery to remove the tumour, in the earliest stages
• Chemotherapy and/or radiotherapy to treat cancer in the more advanced stages