Young Adults
Genetic Testing
We can now do predictive testing, so you can find out before you become symptomatic as to whether or not you carry the faulty HD gene. The decision about whether to be tested can be very difficult. Below you will find some answers to commonly asked questions about the predictive genetic test and genetic counseling. We have only provided some basic information and urge you to make an appointment with a genetics counselor for further information. Remember this is a huge decision, one that shouldn't be rushed. Take your time, be informed, and most importantly talk to others who have been in your shoes.
Some people absolutely want to know, and others are quite clear that they prefer to live with not knowing. Some people also find that they change their minds from month to month, week to week, or day to day. I call it the HD Rollercoaster! It is up to each individual to think about what getting tested means for them, and how the knowledge of having or not having the changed gene will affect their life.
Reasons for taking or not taking the test:
Those who choose to be tested usually do so in order to be able to make informed plans for the future regarding marriage, having children, career, finances and so on. Others may simply crave relief from the anguish of being "at risk." For them, knowing, whatever the outcome, is better than not knowing.
However, experience has shown that while many at risk individuals say they wish to know their gene carrier status, far fewer actually undergo testing. The majority of people find the emotional burden of knowing, or risks to confidentiality outweigh the benefits of learning that they carry the changed gene.
It is important to remember that individuals should not be coerced into testing, whether by a spouse, another family member, a doctor, an insurance company or an employer.
Why must you be 18 to take the test?
There are International Guidelines for testing for HD which advise that the test should only be carried out on a person who has 'reached the age of majority' in their country. The age of majority is the chronological moment when children legally cease to be a minor and assumes control over their persons, actions and decisions, thereby terminating the legal control and legal responsibilities of their parents over and for them. In Canada the age of majority is 18. So, it is advised that young people do not go for the test until they are at least 18. This should not stop any young person who is under 18 seeking help or advice from a genetics or health/social care professional about HD.
Here are some very good reasons for not getting the test until you are at least 18:
To protect a young person's autonomy. This means having the right or power to govern oneself i.e. to determine things for yourself. Research has shown that during adolescence young people may be influenced by many things that can change what decisions they make such as family, friends, or media. Of course this is true for adults too, but young people may be strongly influenced by other people's opinions. In order to avoid this it is advised that young people put off testing until they are older and can be certain that it is their choice to take the test. Overall, professionals want to make sure that people who take the test for HD are choosing to do it themselves, and that they are certain this is the right choice for them.
To protect a young person's privacy. In Canada it is believed that a person's confidentiality should not be broken by a doctor, unless the doctor gets the person's permission or in exceptional cases where the doctor has a duty to report something serious, like child abuse. If a young person is under 18 then other family members may feel they have the right to know the young person's test results. For example, genetic counselors sometimes get asked by parents to test their children because parents want to know if they carry the HD gene or not. As HD is usually an adult onset illness there is no medical reason for telling parents this information when their children are under 18. So people who have a parent with HD have the right to tell their parents their result only if they wish to. Some people choose not to. By advising that young people do not take the test until they are 18 their confidentiality and right to privacy can be fully respected.
To avoid changing the attitudes of a family towards the young person. Research tells us that when a person finds out they are a gene carrier, or not, people's attitudes can change towards them, including family members. For example if you were found to be a carrier of the changed HD gene when you were young your parents may become incredibly overprotective and as a result you don't grow up living a 'normal' childhood.
To avoid other forms of discrimination. Unfortunately we live in a world where people are discriminated against, and people who live in a family with a genetic disorder may experience discrimination e.g. by insurers, employers, peers, in relationships and so on. In order to protect young people who carry the gene from certain types of discrimination it is advised they put off testing until they are at least 18, and are able to think through the impact of possible discrimination.
What is Genetic Counseling? Why do I have to go before I take the test?
The main purpose of genetic counseling is to provide information about HD so that individuals can make informed choices. Genetic counseling should be seen as a process, which means the information will be given over a period of time, usually about 3 months. This means you will be able to talk about the pros and cons of taking the test, and about your specific situation. Once an individual has been given their test result, it is information which cannot be taken back. Genetic counselors want to make sure that someone who takes the test has thought through all the possible consequences and is well prepared before they get their result. This is why the genetic counseling process can take so long. Individuals are also encouraged to take along a person they trust to support them though the process.
What is the test?
The test is a very simple blood test. Your blood sample will be sent to a laboratory to test to see whether or not you carry the faulty HD gene. This usually takes about a month, but in some locations can take several months. Once your results are in, you will once again meet up with the Genetics counselor. No matter what your results are, they will not tell you over the phone.
What can the test tell me?
The result will tell you whether or not you carry the changed HD gene. If you do carry the changed gene then you will get HD at some point in your life. If you do carry the changed HD gene, although the test cannot tell you exactly when the disease will start or what it will be like for you, a genetic counselor can help you interpret the results. If you do not carry the changed gene then you will not get HD, nor will you pass on the changed gene to your children.
What are CAG repeats?
Everyone in the world has an HD gene. The difference is that in people who have Huntington's Disease, the gene is much longer/bigger. The gene has a 'coding element' called a CAG repeat and if this is longer than 36 repeats a person will develop HD at some point in their life. In people without HD the CAG is repeated up to 26 times. For further information on CAG repeats see: http://www.stanford.edu/group/hopes/basics/basichd/a2.html
What is the grey area in predictive testing?
The vast majority of people who carry the changed HD gene have 40 or more repeats and will develop HD. A very small minority may be told their CAG repeat is between 27 and 39. These numbers are called the 'grey area.' These people will still get HD, however the onset may be much later in life and often times these individuals die of other illnesses such as cancer before the HD symptoms begin. That being said there is still a risk of passing that gene onto their offspring.
What about confidentiality?
You might be worried that your details will not remain confidential if you attend a genetics service, but genetic services are as confidential as other medical services. Members of staff will not talk about you to other family members, and vice versa. Some people decide that they do not want their doctor to know they are going for the test, and contact the genetics service directly themselves. You are allowed to do this if you would prefer to.
Having Children
Should I have a baby?
The decision to have children can be huge in anyone's life. Everyone has to decide for themselves whether they want to have children or not. Some people at risk of HD, or who have the changed HD gene, decide they do want to have children. Most hope that by the time their children grow up, there will either be a cure for HD, or better drugs to manage the symptoms. Others decide not to have children because they don't want to burden their children with the risk of HD.
If you are at risk of HD, or you carry the changed gene for HD, and you wish to have children there may be additional areas for you to consider. The two main areas of concern are:
(i) You may pass on the risk of developing HD to your children, and
(ii) Your children will have to witness you going through the stages of HD.
Who can I speak to about having children?
There are many people who are available for you to talk to regarding your decision about having children. These people may include your partner, family, or friends. If you require specialized information, a genetics specialist can help you make the right decision for you and your circumstances.
What is the genetic risk to my children?
If you have tested negative for the faulty HD gene then there is absolutely no chance that your children will contract the faulty gene.
If you test positive for the faulty HD gene then there is a 50/50 chance that your children will be carriers as well.
Reducing the Risk that your child will get the faulty HD gene:
These are your options:
Prenatal Testing, Preimplantation Genetic Diagnosis (PGD), Gamete Donation, and/or Adoption.
Prenatal testing
Prenatal testing involves testing a fetus in the early stages of pregnancy to see if it has the faulty gene for HD. There are two methods used to do this: chorion villus sampling and amniocentesis.
If the fetus does not have the changed gene then the decision to carry on with a pregnancy is straightforward, due to the fact that the fetus is HD free.
If the fetus is found to carry the changed gene there are two options available to you:
- Terminating the pregnancy - which can be a very emotional, difficult and challenging decision to make OR,
- Continuing with the pregnancy knowing that the fetus does in fact have the faulty HD gene. This is further complicated by the fact that you and your child will know from the get go that they will in fact one day develop Huntington's Disease.
Preimplantation Genetic Diagnosis (PGD)
This is a procedure, which uses In-Vitro Fertilization (IVF) to fertilize a woman's eggs with her partner's sperm in a laboratory. The embryos are then tested for the changed HD gene. Only embryos that do not have the changed gene are implanted into the womb. This means the baby will be born with no risk of developing HD. Any remaining unaffected embryos can be stored for later use as required.
However, like all IVF procedures the success rate is quite low (1 in 5) and can be a lengthy emotional process which also carries a significant financial burden.
Gamete donation
This method uses a donated egg or sperm in place of the affected parent. There are different ways to do this, either by using a known donor such as a family member or a friend, or an unknown donor through a fertility clinic.
Adoption
Some people who are at risk of developing HD decide to adopt a child that is not biologically theirs. This way they ensure they do not pass on the faulty HD gene to their offspring. If you are considering adoption it is important to consider that several agencies would question whether or not a parent with HD would be the appropriate environment to raise an adopted child. That being said many have fought this issue stating that the symptoms usually don't occur until later in life, and that there will be a strong family network in place to deal with the changes that are likely to occur.
