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My dad has HD. What are the odds I will?

December 28, 2015

Huntington's Disease Youth Organization

HDYO has more information about HD available for young people, parents and professionals on our site:


My dad has HD. What are the odds I will?

Q. My dad has hd. My older sister and brother have signs of it. Me and my other older sister don’t not yet anyway. I look and act exactly like my mom. I’m very organized and have s good memory what are the odds I will have it?

Caitlin, Young Adult, USA

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A. Dear Caitlin, Many thanks for your email. I am sorry to hear about your dad, and that your brother and sister may have signs of HD.

You’re probably aware that HD is caused by an expansion (of the ‘CAG repeats’) in the HD gene. When someone with an HD gene expansion has a child, there would be a 50% (1 in 2) chance that the child would also carry the HD gene expansion, in which case we would expect them to develop symptoms of HD at some stage in their life. (You may also find this HDYO article helpful http://en.hdyo.org/pro/articles/50, as it describes how the gene can be passed on in families in more detail.)

Therefore, thinking about your question, when you were born the chance that you inherited the HD gene expansion would have been 50%. I’m afraid that the fact you are more like your mom does not reduce this chance. This is because the HD gene is just one of around 30,000 genes that we all carry, and many genes (inherited from both sides) are involved in appearance and behaviour characteristics.

It is good to hear though that you have no concerns about your organisation or memory skills. The longer someone at risk of inheriting the gene lives without developing any signs, the less likely they are to have inherited the HD gene expansion. However, as you are 26, unfortunately at this point it is unlikely to reduce the 50% chance by all that much, as the majority of individuals who carry an HD gene expansion would not have any symptoms until quite a bit later in life (the average age of onset is around 35-50, although this can be variable and some people do develop signs earlier or later in life than this).

I hope this helps to answer your question, but please do not hesitate to get back to us if you have any queries. Often people at risk find it useful to see a Genetic Counsellor or Doctor, who could give you more information, tailored to your family, as well as discussing your options. If this is something you would be interested in, this website may help you to find your local Genetics service.

Best wishes