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If my brother's baby doesn't have HD will I get it?

March 28, 2015

Huntington's Disease Youth Organization

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

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If my brother's baby doesn't have HD will I get it?

Q. I have a question concerning if I’ll be a carrier of this disease.

My grandma was the one with Huntingtons and had two daughters my mother and my aunt. Both of them don’t want to get tested for reasons understood. My mother has a 22 year old son who recently had a baby and the baby got tested for hd and came back negative. does this mean my brother got lucky. Does this mean I won’t get it at all?

Marc, Teen, USA

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A. Dear Marc,

Many thanks for your question.

To answer your question I first of all need to explain how HD can be passed on in families. As you may know, HD is a genetic condition, caused by an ‘expansion’ in the HD gene. If someone who carries an expansion has a child, there is a 50% chance (1 chance in 2) that the child will inherit the expansion (there is then a separate 50% chance for each further child they have – so if someone has 2 children it does not mean one child will inherit it and the other won’t).

Therefore, thinking about your grandmother, if she had the HD expansion, your mother would have had a 50% chance of inheriting it (and equally a 50% chance that she didn’t).

While it is certainly good news that your brother’s baby does not carry the expansion, unfortunately it doesn’t really change the situation much for you, as your mother (and also your brother) could still carry the HD gene expansion even if your brother’s baby doesn’t.

I hope that makes sense. If you would like to read more about the HD gene expansion and how it can be passed on in families, you may find this HDYO page useful.

If you would like to discuss this further, it may be helpful to see a genetic counsellor or doctor, who could go over your family tree and explain the inheritance of HD in more detail. If you would like to arrange this, this site may help you find your local genetics service.

I hope you find this information useful, and please do not hesitate to get back in touch if you have any further questions, or if you have any difficulty locating your local genetics centre.

Best wishes

Bill