[www.hdlf.org]
According to this article, children could be symptomatic for JHD with CAG's between 45 and 58. It is interesting because there are adults with those numbers (the lower ones for sure) that aren't symptomatic. I know the CAG count is just sort of a guide... itdoesn't always mean anything...meaning someone could be a 36,37,38 or 39 and develop symptoms or not. And you could have 2 people with identical numbers with different ages of onsets and different presentations of symptoms. I guess I'm just posting this because it seems confusing to me how dramatically different people can be in their presentation and onset.

Most of the people I know of with CAGs in the 40's are adult onset.

I think JHD is more typically seen when the CAG is in the 60-80 range. JHD is classified as onset of symptoms before age 20. In some cases, a lower CAG along with other condition such as brain injury can bring symptoms on sooner.

HDSA has a great brochure on JHD.

PattyC

I am the wife of a man with Huntington's Disease and mother of 2 at risk. Our family likes to be involved in HDSA events and fundraisers. I am also an OT and work in home health.

I think that if someone is at risk and is clinically diagnosed with HD and the CAG count is positive, I would disregard the number.

An early article about testing for JHD that we covered here on the Lighthouse reported on the results of genetic testing on children clinically diagnosed with JHD. Some tested negatively meaning that their symptoms had to have been caused by something else. (I know of two cases personally where this happened, For example, we had a poster here whose grandchild had multiple neurological symptoms that could have been JHD but he tested negative and therefore he didn't have have it.) Some tested positive with CAG scores above 60 and they were accepted as genuine JHD patients. However, some tested positive with a CAG count below 60 and they were classified as nonsymptomatic for JHD but symptomatic for a yet to be diagnosed disease. Well how did they know that CAG counts HAD to be 60 or more? They didn't really; this was an early conclusion based on a sample sample of JHD patients and what the study above is saying is that if children have symptoms and they continue to get worse and more symptoms appear until it is obvious to everyone that they have Huntington's Disease, didn't they have it before? It took an average of nine years for those children to get their HD diagnosis. If we wait until a disabled child is an adult because someone arbitrarily decided that their CAG count is too low to be JHD, they will miss out on government benefits, they will be stigmatized in school for not trying hard enough or being a behavior problem and they won't get an accurate IEP. If two adults with the same CAG count can have an onset decades apart, then why arbitrarily decide that certain children who are HD positive and having progressively worse HD symptoms can't actually be sick with HD?

What researchers now know is that there are modifying genes which can cause onset to be earlier or later than average for the CAG count. As Patty pointed out, brain injuries can bring on an earlier onset and we also know that environmental conditions can make a difference.

Thanks Marsha. You put this confusing issue into words that make sense. I too think that the CAG sometimes clouds the issues especially if that is the primary thing physicians are looking at. I like how this study pointed out that the average wait to get a diagnosis was 9 years...that is really sad and hopefully this will change so kids can get help earlier.
I am having a dilema because my son has some issues that are probably not HD related (he is at risk), but possibly it could be HD related. He needs a medication change, but I have been dragging my feet and am really frightened because I don't want to make him worse. I ask myself, "What if I knew if he was HD+? How would that change his medication management?" I'm not sure. Part of me would like to find out his status and then use some sort of grading system to help make the medication decissions. I was thinking the CAG would be a guide so that if it was in the adult range, I could be relatively safe in giving him some meds that are commonly used (usually with minimal side effects) such as stimulants, but if the CAG was higher I would definately steer clear of those since there was a case study showing it was contra-indicated in this case. That would lead me to use the drug(s) that are a little "stronger" (such as anti-psychotics with more side effects) but that might be safer for a JHD brain. Does that make sense? But as you can see, based on this article, I'm not sure what would be an accurate method of making the decission even if I knew if he was pHD. Part of me really wants to know and have him tested, but the other part is aware of his right to privacy. It seems there is really not much research out there for knowing what medications are contraindicated with HD which makes it even more frustrating to know the best way to help my child.
Thanks for letting me vent about this. This has been causing horrid stress with me for awhile. My child is young (under 10) and is the treasure of my life. He does need some extra help but I don't want to hurt him.