Huntington’s is a weird genetic disease.
If my fetus has the critical number of CAG repeats for Huntington’s, I’d abort. Yes, we all die of something, but there is a difference between knowing that your death is extremely likely to be slow and excrutiating for both yourself and your loved ones versus not knowing. Since life is already so incredibly unfair even when a person is dealt a “normal” genetic hand, I think it is quite reasonable to take control over those few things you can. Terminating over something like this is completely aligned with my personal values and ethics.
There would be no dilemma for me over a clear-cut diagnosis. If there’s absolute certainty that the baby will develop Huntington’s, I wouldn’t hesitate in my decision. But I probably would if the risk was more like 35 or 40%.
This is impossible, you say? No it isn’t! I got tested for Huntington’s a few years back when I pursued a diagnosis for my tics (adult-onset motor tics is a symptom of HD). I got a report back that enumerated the CAG repeat lengths I have on my two huntingtin loci. I have a slightly elevated number on one of my chromosomes while still being below the threshold of real concern overall. But according to the report, my great-great grandchildren are at risk!
Why? Because the gene is especially vulnerable to mutation. With each generation, the number of CAG repeats has a tendency to expand by a small amount. It is a sure-fire thing? No. Just a tendency. So my future generations are at small but discernible risk of suffering from the disorder, even though I have no known family history of it…simply because one of my chromosomes has a moderate number of repeats–just waiting for a couple more mutations to put it over the edge into the “high risk” category.
So…it is really not sufficient to determine your risk simply by asking the person you’re mating with about their family history. Both you and your mate’s chromosomes may have well below the critical number of CAG repeats (in that case, your offspring would be in the clear) or both of you may have a chromosome with a moderate to high number of repeats (in which case, your offspring would have a low to high risk of developing the disease). And just because your kid doesn’t develop the disease does not mean their children will not, given the way the genetics work.
I was upset when the doctor insisted I get tested. I thought I knew all about genetics, and I’d always been taught that you’d absolutely know it if you were at risk for Huntington’s as long as your parents lived to middle age. But I quickly understood how wrong this assumption is! Sometimes the symptoms don’t kick in until later in life (past middle age), particularly if the patient doesn’t have a super long CAG repeat length. Or they have a subtle form of the disease. And when either/both of these two things happens, the disease can be mistaken for something else. Or a person can start exhibiting the beginning stages of the disease in their 40s, but wind up dying from something else before anyone even considers HD. So it is possible that HD cases might go undetected in a family rife with chronic mental illness and health conditions, thereby preventing an individual family member from knowing they are at risk. This is why testing is so important.
I’m kind of glad I went through the experience of getting tested because I learned a lot from it. It is also taught me that evaluating risk is tough (at least for me). Like any fifth grader, I can grasp 50:50 very well. But 70:30? Nope. And then there’s all the interesting (and headache-inducing) ethical questions. Just how far down the family tree should a person be concerned when evaluating risk? Is it ethical to have children knowing that their children might be at elevated risk of the disease? If my test indicates that my grandchildren might be at risk, am I obligated to tell my children this? At what risk level is someone obligated to say something to other family members so folks can at least know whether they should get tested? It’s such a tricky situation. I’m relieved it is just a navel-gazing exercise for me and not something I have to really act on.