Does having a low gene count decrease the chances of HD?
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Q. Does having a low-Huntington gene count decrease the likelihood a child will develop HD?
Laura, Young Adult, USA
A. Hi Laura,
I may not have fully understood your question, but generally what you say is true. It would be good to know what you mean by ‘low’. For example a CAG repeat count <35 is consistent with an individual not going on to develop HD. The other key point is that a child developing HD is very rare. Most individuals with the HD gene fault will have an onset of symptoms mid adulthood (around 35-45 years). In the rare case of childhood onset, there is usually a history of early onset in the family, and typically where the father has started with symptoms in very early adulthood. Whilst it is not possible to predict age of onset by the number of CAG repeats (only accounts for ~ 50% of the variance), childhood onset is usually associated with a longer CAG repeat length (usually considerably more than 50 CAG repeats). You might find this article in HDYO useful.