I have a couple of questions about HD. How does a doctor predict age of onset? Is there a genetic link, or is it strickly an individual matter? Is there ever a case of a child being diagnosed before a parent shows symptoms? Also are there milder forms of HD, or are all cases as severe as I have read about? Thanks

Beside having the same name we have the same questions floating around in our heads.
My hubby is in the diagnosis stage of this something that has invaded our lives.
His uncle died with Huntingtons many years ago........
Dad has symptons we think...but not diagnosis.

email me personally and we can compare notes and thoughts.
Diane.....

Diane: We had a trauma in our family about ten years ago. My sister and I already were suffering from really early symptoms. We hadb\n't spoken to any one else in the family about our short term memory loss yet. It seemed like it would pass. Our father, who has really severe symptoms compared to my sister and I has never yet admitted that it is anything except natural aging. I think we all started to notice changes in our minds and bodies about the same time. Holly

I was told by the genetic's dept. at Baylor that they do not go against protocol and test children under age 18 = the at risk parent will be tested first. They almost "never" test children unless they have visible symptoms. This is a real beef with me. I think as a parent, I should have the say so if I want my child tested before age 18. Don't get me on that soap box!! But, I have wondered the same thing...is it possible for a child to exibit symptoms before the parent...I would like to know. If you find an answer, please email me. Thanks.

To: Diane
ref.: question -"Also are there milder forms of HD, or are all cases as severe as I have read about?"

My pHD father started symptoms long before we knew he was even at risk. He never had "the shakes" or any physical involuntary movements. His were the behavioral problems. The fact he was an alcoholic didn't help. I have not read much about pHDs that get the "emotional" symptoms, but I believe it is better to get the help one can to overcome the mental torment. There are articles I've read where some pHDs actually experience onset after 60. Best thing you can do is contact HD organizations where you can trust their discrepancy and rely on their knowledge.

(I typed in a response to your first question and lost it while trying to get back to your subsequent questions. I feel very klutzy this a.m. I'll try again.)

1) How does a doctor predict age of onset? Every gene is composed of just four different chemicals. I don't remember their names, but their initials are C, A, G, and T. In the HD gene, there is a stretch that goes "CAGCAG . . . CAG". This stretch is called "CAG repeats". The number of repeats determines whether HD will occur: Less than 35, no HD; greater than 40, HD; in between, a "gray area" where it may or may not occur.

The researchers who discovered the gene also noted that there seemed to be a relationship between number of repeats and age of onset (the age at which symptoms appear)--the more repeats, the earlier the person becomes symptomatic. E.g., a person with 41 repeats might not become symptomatic until 50 or 60, while one with 100 repeats might have the juvenile form. (In fact, I recently read of a person with 117 repeats who did have the juvenile form.)

The researchers did some statistics and discovered that there was a statistically significant correlation between repeats and age of onset, but only a weak correlation, accounting for only about 60% of the variation in age of onset, the other 40% being caused by other factors, perhaps other genes or environmental factors such as stress, trauma, poor health, etc. Thus, a doctor can use a person's repeats (obtained via the HD gene test) to get a rough idea of when the person could become symptomatic.

2) Is there a genetic link, or is it strickly an individual matter? I'm not sure exactly what you mean by a "genetic link", but there is a tendency for age of onset to be similar for affected members of a family group. This is because the number of repeats is pretty much the same for parent and child. (There is more variation if the parent is male, the number of repeats often increasing, resulting in earlier symptoms in offspring than parent.) However, I've heard several researchers say that, if you look at a large enough family group, you'll find every age of onset from early (juvenile) to late.

3) Is there ever a case of a child being diagnosed before a parent shows symptoms? Yes, but it's rare--usually the affected parent is the father.

4) Also are there milder forms of HD, or are all cases as severe as I have read about? Every case is different, and some people, often those with late onset, have milder symptoms. However, they all progress, and if the pHD lives long enough, he/she will become almost completely incapacitated. Juvenile cases are very severe and progress rapidly. My mother became symptomatic at 60 and died at 75 of breast cancer but was still pretty functional up to the end.