My mum does not want to test, can I have JHD?

Q. My grandmother has Huntingtons and we are not sure if my mom has it or not because she does not want to get tested but if she does have symptoms, in our family usually happen at around 40 or so. I am wondering is it still possible that I could have Juvenile Huntingtons

Seth, Teen, Canada

A. Dear Seth,

Thank you for your question.

Given what you have said, it is very unlikely that you would be at risk of developing the juvenile form of huntingtons. Juvenile HD is relatively uncommon (affecting less than 10% of people with HD), and is more likely to happen if the parent has been affected at a young age, and/or when a child has inherited the HD gene expansion from their father (this is because when the HD gene is passed from a father to a child, sometimes the expansion can get bigger, which can increase the chance of juvenile huntington’s). This is described in more detail in this HDYO article.

Therefore, even if you have inherited the HD gene expansion from your mother (which we would currently estimate to be a 25% chance), the gene is unlikely to be in the range that would carry a risk of juvenile HD, given that you said most people in your family have been around 40 when symptoms have started.

I hope this helps answer your question, and you find this of some reassurance. Please do not hesitate to get back to us if you have any further questions.

Best wishes

Bill