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Is it almost 100% that my friend or her brother will have HD?

March 25, 2016

Huntington's Disease Youth Organization

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Is it almost 100% that my friend or her brother will have HD?

Q. One of my friends dad just recently died from Huntingtons disease. My friends mom was not infected but her dad obviously was. Her parents had two children, is it almost possible that her brother or my friend will 100% chance have the disease?

Shelia, Young Adult, USA

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A. Dear Shelia,

Thank you for your question. I am sorry to hear that your friend’s dad died of HD recently.

If someone with HD has a child, there is normally a 50% chance that the child will inherit the HD gene change. The 50% chance is exactly the same for each child, so if they have two children it does not mean that one will definitely inherit it. It’s a bit like tossing a coin – if it comes down heads it doesn’t mean that it will come down tails the next time you toss it.

So, your friend will have a 50% chance of inheriting it, and her brother will also have a 50% chance. It may be that both of them inherited it, or neither of them, or just one of them.

I hope this helps answer your question, but please just get back to us if you have any further queries.

All the best,

Bill