Hi there
There is supposedly incomplete penetrance. I have been trying to get statistics but different studies say different things. The best I found was 70 percent but most say mid nineties for some neuro degenerative disease mostly ALS but you could get dementia or progressive supranuclear palsy. The good news is they are working on gene blocking for c9 hope to start clinical trials next year. Check out c9ID on FB
Consider being part of preFALS studies if you are c9 positive. The only way we are going to beat this is through research
Best
Nikki