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Lynch syndrome is an inherited condition that makes people more likely to develop particular types of cancer. In order to explain Lynch syndrome, we need to explain how normal cells work and divide, and how cancer occurs


For our body to grow and repair itself, cells must create new cells. If you cut yourself, your skin cells continue to divide until the wound is healed. Normal healthy cells know when to stop dividing. Cancer happens when cells continue dividing when they are supposed to stop. As the cancer cells grow, they begin to crowd out normal cells and eventually form a lump. A lump of cancer cells is called a tumor.


There are some mechanisms in our body that protect us against cancer. These mechanisms guard cells and make sure that the cells know when to stop dividing. When these mechanisms identify cells that are unable to stop multiplying, these mechanisms repair or remove these cells, and by doing so they prevent cancer from occurring. One of these mechanisms is created by the DNA mismatch repair genes called MLH1, MSH2, MSH6, and PMS2.


Everybody has these genes. In Lynch syndrome, one of these genes is not working properly. This means that their cancer protection mechanism is not working at 100%, and so people with Lynch syndrome have less protection against cancer.


These mismatch repair genes work like police officers in our body, checking that cells are made properly and don’t divide and multiply out of control. If these genes aren’t working properly, it might result in fewer police officers, which results in less protection against cancer.


This means that people living with Lynch syndrome have less protection, rather than having a genetic alteration that causes cancer itself. For this reason, not all individuals living with Lynch syndrome will develop cancer, but having less protection makes it more likely. Most people living with Lynch syndrome live a normal life.


Lynch syndrome is caused by a genetic change in one of these DNA mismatch repair genes called MLH1, MSH2, MSH6 and PMS2. There is a fifth gene involved called the EPCAM gene because it turns off the neighboring MSH2 gene. EPCAM alterations are very rare and only account for 6% of Lynch syndrome cases.


The main concern in Lynch syndrome is colorectal (bowel) cancer. For women, endometrial (womb) cancer is also a concern, and to a lesser degree ovarian cancer. There is a small increase in the likelihood of developing a few other cancer types that you may need to keep an eye on, but this will be explained later. The risk or likelihood of developing different cancer types depends on which gene is implicated, and other factors such as gender and age

Having a diagnosis of Lynch syndrome can be a double-edged sword. On one hand, it could be worrying to know that you have a higher likelihood of developing cancer. On the other hand, you are armed with knowledge and an enhanced screening program that will help you prevent these cancer types and live a normal and fulfilling life. It will empower you to manage your care. Monitoring and screening will help to prevent cancer or help to diagnose and treat it early. It is important to know that you are not alone. As many as 1 in 278 people live with Lynch syndrome.


There are over 7 billion people on earth. Over 25 million of them have Lynch syndrome, just like you. If you would like to meet other people living with Lynch syndrome, Lynch Syndrome UK will be able to support you. We are a charity association run by people living with Lynch syndrome. We have useful resources, organise events, and have online as well as face-to-face support groups where you can meet people just like you

How did I get Lynch syndrome?


To understand how Lynch syndrome happens, we need to understand DNA and genes. DNA is the code our bodies use to make genes. Genes are the instructions that tell our body how to grow and develop, and each gene has its own job to perform. Some of our genes determine what hair and eye colour we have, and some are responsible for protecting us against diseases like cancer.


Inherited conditions are due to a genetic change (also known as a variant or genetic alteration) in a particular gene, which can be passed on in a family. A genetic change may alter the level of protection a family has against certain diseases such as cancer.


Lynch syndrome is usually caused by a genetic change in the mismatch repair genes. Mismatch repair genes protect us against cancer by repairing DNA mistakes that can occur when our cells are made. The Lynch syndrome genes are like police officers in our body, checking that cells know when to stop dividing and do not turn into cancer cells, and by doing so they protect us against cancer. If these genes aren’t working properly, this might result in fewer police officers protecting us against cancer.


When we are conceived, we inherit two copies of every gene, one copy from our mother and one copy from our father. If one of our parents has Lynch syndrome, at the point of conception, they have a 50% chance of passing on their altered copy and 50% chance of passing on their unaltered copy. If a person inherits the altered copy, they will have Lynch syndrome. This is also known as an autosomal dominant inheritance pattern. This also means a person with Lynch syndrome has a 50% chance of passing on their altered gene each time they have a child.

Mismatch repair genes are inherited from your parents. If you inherit an altered copy of the gene that causes Lynch syndrome, you have Lynch syndrome. Luckily, the copy 4 from the other parent may work just fine. However, there is a chance that one day your working mismatch repair gene will make a mistake in one of the organs affected by Lynch syndrome.

When both of your mismatch repair genes are no longer working, you have less protection against cancer, and so cancer will be more likely to occur. In 99% of cases, you would have inherited Lynch syndrome from one of your parents. In this case, it is possible that your siblings will have it too. If you do not have Lynch syndrome, you cannot pass it on to your children because you cannot pass on something that you don’t have.


It is possible to have Lynch syndrome without inheriting it from your parents, but this is extremely rare. In this case, the genetic alteration happens by nature after conception, and you are the only one who has it. This is called a ‘de novo’ genetic alteration. This would be the first time that Lynch syndrome is found in the family. For this reason, your siblings and parents are unlikely to have Lynch syndrome, but your children will have a 50% chance of inheriting the alteration

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