I have a family member getting ready to be tested. Two questions ... if you have the HD gene, is it 100% that you will have the disease and all it's symptoms? Can one not have the disease and yet be a carrier for the next generation? Thanks for any answers.

Each family member has a 50% chance of inheriting the HD gene. If you have the HD gene and the repeat count is 40 or above you will get HD. The only way to be a "carrier" is to have a repeat count between 30-40, I think, and then the next generation might inherit a higher repeat count.

There are probably other people who can explain better.

Stacy-NJ

Ivy, Stacy is right. If a person tests positive for hd, and if their CAG is 40 or higher, they will get hd at some point in their life for sure.

Depends on the CAG Repeats. From [www.ninds.nih.gov]

<28 Normal range; individual will not develop HD

29-34 Individual will not develop HD but the next generation is at risk

35-39 Some, but not all, individuals in this range will develop HD; next generation is also at risk

>40 Individual will develop HD

The way I see it over 28 and you have an unstable gene but might never become symptomatic. Over 40 and you will become symptomatic (hopefully medicine can help here in the near future). An unstable gene can also mutate when passed on. We expect that is what happened with my grandparents. Neither showed any symptoms and passed away in their 70's and 80's yet my father has repeat of 43 and became symptomatic in his 60's and my repeat is 41. Typically gene mutation is more prevalant when being passed from the male side.

The symptoms also vary from person to person. I have been trying to find links between CAG repeats and age of onset but I have not been able to find any with a large amount of certainty.

Here is a site that has a lot to say about age of onset - [www.ncbi.nlm.nih.gov] Note that even identical twins have a large variation in their ages of onset. This is actually a very hopeful sign - it suggests that environmental factors such as diet and drug use can indeed play a significant role in managing the disease, positive and negative.

Hi lv2,
This question seems to be one of the most frequent that come up,the answers can vary though.There have been explanations of this already on this thread,how the cag repeats affect the possibility of onset.Unfortunately with HD there is nothing 'set in stone',we are still discovering new things about the disease.Occasionally there is one that 'breaks the mould'.I know that there has been some work done on this in Italy recently,and that the results will be published shortly,I eagerly wait for this.As soon as I get informed of this I will gladly pass on the link.Until then I dont want to talk too much about things that are uncertain to me (no point in me rambling if I am wrong).
Take good care.
Gordon