Genetic disease

Have you ever wondered if your genes have a surprise in store for you? The advances made over the last few years in genetic testing now mean that it may be possible to test for a number of diseases and that a prediction of your risk of contracting the disease may be calculated. This can have both disadvantages and advantages; on the one hand you might want to know if there is a strong possibility that something could be done to prevent you developing the disease in the first place, or if there were to be good treatment available once you became ill. But it could be a real disadvantage to know if you are going to develop a condition for which nothing can be done. Then there is the insurance issue. There have been fears that if your risk of developing a condition is high, it may be the case that no-one would offer you insurance. So whilst prior knowledge may be a good thing, there certainly can be downsides which need to be fully considered before anyone undergoes genetic testing.

Genetic testing can be offered for conditions caused by faulty genes that may cause an illness but which has not yet developed, such as Huntingdon's disease, or to inform you that you may have a higher risk than the average of developing some cancers.

Genetic counselling may be useful to help couples contemplating pregnancy where there is a family history of a condition such as cystic fibrosis, sickle cell disease, thalassaemia, haemophilia (to name but a few). In some conditions such as sickle cell disease, people may carry the disease but do not suffer from the illness and would only pass the condition on if they were to become pregnant by someone who was also a carrier.

Cancer
Around 5-10% of breast and ovarian cancers are thought to have a genetic cause. Two main genes have been identified, known as BRCA1 and BRCA2 (breast cancer 1 and breast cancer 2). If there is a fault in BRCA1 or BRCA2 it can increase a person's chances of getting breast cancer, but does not mean it will definitely occur.

Generally referral for specialist genetic counselling is normally only appropriate for women at a high familial risk of breast cancer. Genetic testing may then be offered. If it is discovered that you have one of these genes, then your options will be outlined to you. You would be offered early screening by mammogram. Screening by MRI scanning may be possible in the future, which would be particularly useful for younger women under the age of 35 as mammograms are not very sensitive in younger women. Some women whose lifetime risk of developing the disease is very high are offered bilateral mastectomies. Even this is not foolproof as it can be difficult to remove all the breast tissue.

Women with a high risk of developing ovarian cancer can be offered screening by trans-vaginal ultrasound.

Huntingdon's disease – would you want to know?
This is a rare but fatal neurological illness causing involuntary movements, severe emotional disturbance and a decline in intellectual functioning. The manner in which it is inherited means that each child from an affected parent carries a 50% risk of inheriting the illness. Unfortunately, it does not always become apparent that someone is suffering from the illness until their forties, by which time they have already had children. There is no treatment or cure. Some people choose to be tested in order that they do not pass the condition on, (by not having children) even though it means that they will know the unpalatable truth about their own future.

Downs syndrome
This is a condition in which one of the chromosomes is affected during the process of conception. It causes certain physical characteristics, learning disability and associated medical conditions such as heart defects and an increased risk of leukaemia. It can be tested for during pregnancy and this gives parents the choice of whether or not to continue the pregnancy.

You can see from the above examples that some conditions can be tested for and will actually identify for certain whether someone is affected, eg Downs syndrome and Huntingdon's disease. In other conditions, it is only possible to give a prediction of the risk that you or an unborn child might be affected. As research continues, it will no doubt be possible to be more accurate and for more conditions to be identified. The usefulness of this will always be limited by whether anything can be done to help, once you have the bad news.

Further information

Genetic testing and counselling

Cancer Backup

This article published on
08 February 2006

Next review date 2/1/2013

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