Given the way people used to have kids, until fairly recently, people would be past their child bearing years when they figured out they were sick. So it was too late not to have kids. And all those kids had a 50-50 chance of getting Huntingtons themselves when they were older. So you had the horror of knowing you were going to die - and that your kids might have it too.
There is a genetic test, but there's little in the way of treatments and there is no cure.
Years ago, I wanted to write a novel about a guy who thinks he has Huntingtons (because he watched his dad die from it), but really has Tourettes (which has happened). Once he receives the news that he isn't gene-positive, his life goes into a tailspin. Jack is in his 30s and has wasted his life because he never thought he would get a chance to live it.
In researching the book, I found an online group for people dealing with HD or just wondering if they had it. It seemed like a good way to learn more about it. There were several women who were caring for a husband with HD at the same time as they cared for children with an even worse form, juvenile HD. One woman once posted to ask people to take care of her cats and then was never heard from again. There were stories of murder-suicides, as spouses reached the breaking point. People debated about having the test, or debated having children without having the test.
After a while, I began to feel like a lurker. I finally came out of the closet. Some people reacted very negatively, which I could understand. Some people embraced me, hoping that I would get the word out.
And while I loved the book I wrote, my agent was less enthusiastic, fearing it was a "tweener" and didn't fit into any genre niche. The first six editors who saw it passed. And we shelved it, thinking that my next book needed to get some traction in the marketplace.
Which it did.
But I still think about Jack from time to time.