Huntington's disease Q&As
Published by Bupa's health information team, April 2009.
Answers to questions about Huntington's disease
This section contains answers to common questions about this topic. Questions have been suggested by health professionals, website feedback and requests via email.
- If someone is carrying the gene, is there any way to prevent Huntington's disease from developing?
- What's involved in genetic testing?
- My parents don't have Huntington's disease and there is no history of it in the family, but my dad's sister has just been diagnosed with it. Am I at risk?
- How long do people with Huntington's disease live for?
If someone is carrying the gene, is there any way to prevent Huntington's disease from developing?
No, if you have inherited the faulty gene, you will eventually develop the disease.
Explanation
Genes are bits of code inside each of your cells that tell them what to do. Your genes determine characteristics such as your hair and eye colour and act as a plan for how your body grows and develops. In particular, each gene acts as an instruction for your cells on how it should make proteins, the building blocks of body tissues such as muscle, skin and nerves. Different genes are active or inactive - 'turned off' - in different cells throughout your life.
In Huntington's disease, a faulty gene leads to production of a harmful form of protein called huntingtin in the brain. This faulty gene is called a mutation and it can vary in length. This has an effect on the age at which you develop the disease and how severe it is - the smaller the mutation, the more likely it is that you won't develop the disease until later and the symptoms may be milder. The size of the mutation can change between generations.
Currently there is no way to turn off the faulty gene and stop your cells from making the harmful protein. Research is being done to try to find a way of doing this, but it may be many years before an effective treatment that prevents or treats Huntington's disease is developed.
Sources
- Farah MH. RNAi silencing in mouse models of neurodegenerative diseases. Current Drug Delivery 2007; 4:161-167
- Pineda JR, Rubio N, Akerud P et al. Neuroprotection by GDNF-secreting stem cells in a Huntington's disease model: optical neuroimage tracking of brain-grafted cells. Gene Therapy 2007; 14(2):118-128
- The Huntington's Disease Association. www.hda.org.uk, accessed 19 September 2008
What's involved in genetic testing?
If you're over 18, you can choose to have a genetic test. You will have samples of blood taken from a vein in your arm and these are tested in a laboratory to look for the faulty gene.
Explanation
Finding out that you have the gene for Huntington's disease can be very difficult to come to terms with. Therefore, you may decide not to be tested because you would prefer not to know about something you can't change.
However, if you would rather know whether or not you have inherited the faulty gene, once you're over 18 you can ask your GP to arrange an appointment for you at the genetics clinic in your region. The decision to be tested should be voluntary - don't feel under pressure from anyone.
At the clinic you will first have some counselling about what the tests could mean. This will involve discussing issues such as how you would cope with any bad news and to who and how you would pass on news of the results. It's important to be aware that this type of testing can be emotionally very difficult. The results may offer great relief if they are negative, but if positive, they may change your views on future life, for example to do with employment, marriage and having children. It may also affect how you feel about yourself and your family. You may wish to ask a friend or relative to support you during the testing process. Your GP may be able to refer you if you would like to speak to a genetic counsellor.
If you do decide to go ahead, a sample of your blood will be taken and sent off for tests in a laboratory to see whether you have the Huntington's disease gene. A second test is done at the same time to make sure of the result. It may take several weeks for the results to be available.
If you wish to find out whether your unborn baby has the gene for Huntington's disease, there is a test that can be done towards the end of the first trimester of pregnancy. This involves taking samples of the amniotic fluid that surrounds the baby in the womb, or from the placenta. These are then tested in a laboratory. There is a small risk that having this test could lead to miscarriage.
Not everyone agrees that testing after a baby is conceived is a good idea. In general, people who know there is Huntington's disease in their family are advised to have genetic counselling before getting pregnant.
Another option is to have in vitro fertilisation (IVF) to create embryos that can be tested so that only those that don't carry the faulty gene are placed in the womb. This is called pre-implantation genetic diagnosis. In the UK it's only available at certain clinics licensed by the Human Fertilisation and Embryology Authority and to parents who already know whether or not they carry the gene for Huntington's disease.
Further information
- Human Fertilisation and Embryology Authority
www.hfea.gov.uk - The British Society for Human Genetics
www.bshg.org.uk
Sources
- Duncan RE, Foddy B, Delatycki MB. Refusing to provide a prenatal test: can it ever be ethical? BMJ 2006; 333:1066
- International Huntington Association and the World Federation of Neurology Research Group on Huntington's chorea. Guidelines for the molecular genetics predictive test in Huntington's disease. J Med Genet 1994; 31:555-9
My parents don't have Huntington's disease and there is no history of it in the family, but my dad's sister has just been diagnosed with it. Am I at risk?
There is a risk, but it's much lower than if one of your parents is affected. You would need to discuss your individual circumstances with a genetic counsellor.
Explanation
The gene that causes Huntington's disease comes in different forms. It seems that the longer the gene, the more likely it is to cause Huntington's disease. In some people, the gene can be longer than usual but not quite long enough to trigger the disease. This gene can also be unstable, which means that instead of passing on an exact copy of their own gene, a parent passes on a longer or shorter version. When a longer version is passed on in this way, an unaffected parent can conceive a child who carries the faulty Huntington gene and who goes on to develop the disease. This helps to explain why Huntington's disease can appear in a family where nobody has previously had the condition.
If your father's sister is affected by Huntington's disease, it's possible that your father could be carrying the unstable form of the gene. You may wish to consider having genetic counselling and testing for yourself.
Sources
- Walker FO. Huntington's disease. The Lancet 2007; 369:218-228
How long do people with Huntington's disease live for?
People with Huntington's disease usually live for 15 to 20 years after the first symptoms develop.
Explanation
The age that a person will be affected is linked to the length of the faulty gene. The longer the gene, the earlier the symptoms will start. However, whenever the disease starts, the survival time from the first symptoms is usually 15 to 20 years. As the disease progresses, coordination, falls, malnutrition and exhaustion become increasingly serious. Death is generally caused by heart failure or pneumonia, which results from not being able to control swallowing.
Further information
- The Huntington's Disease Association
www.hda.org.uk
Sources
- Gil JM, Rego AC. Mechanisms of neurodegeneration in Hungtington's disease. Eur J Neurosci 2008; 27:2803-2820
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This information was published by Bupa's health information team and is based on reputable sources of medical evidence. It has been peer reviewed by Bupa doctors. The content is intended for general information only and does not replace the need for personal advice from a qualified health professional.
Publication date: April 2009
Huntington's disease health factsheet
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