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Can you have the mutant gene but not get HD?

February 27, 2016

Huntington's Disease Youth Organization

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


Can you have the mutant gene but not get HD?

Q. Is it possible to carry the mutant gene and not to suffer from the disease?

Jose, Young Adult, Colombia

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A. Dear José

Many thanks for your question. If someone has a ‘full expansion’ of the HD gene, they would be expected to develop symptoms of HD at some stage in their life. The average age at onset of symptoms is around 35-50, but a minority of individuals do develop symptoms later (or earlier) in life than this. So, some people with the HD gene do live into later life before developing HD.

In addition, some people have a smaller expansion of the HD gene – sometimes called an ‘intermediate’ result. Of these, individuals in the ‘reduced penetrance’ range (36-39 CAG repeats) may not develop symptoms of HD at all, or may develop them only in old age.

You can find more information about the different size HD genes in this HDYO article

I hope this helps answer your question, and please do not hesitate to get back in touch.

Best wishes