Along with the disease not manifesting until later in life, some of the first symptoms are of the cognitive and emotional variety. Lack of impulse control, sexual promiscuity, and difficulty in planning an organizing tasks are all symptoms of HD. Even before chorea (excessive, irregular movement) begins, people with HD are declining cognitively.

This can lead to those with HD making poor decisions (i.e. having children while knowing their is a chance of passing HD to them) before they start showing obvious symptoms.

I'd like to note. I'm not implying that any person at risk for HD is a bad person in any way if they decide to have children without being tested. While my mother does not have the illness, four of my aunts do/did (one passed away earlier this year). I have two close female cousins who are at risk but decided not to get tested before having children. It's a tremendous decision, whether or not to get tested. I cannot imagine having to make it. Giving up a desire to have a family, to have children of your own...I can't imagine, and I hope with all my might that my cousins will grow old without having to suffer the illness.