Huntington's Disease

The premise regarding Huntington's disease is simple. A child of an affected parent has a 50% chance of inheriting the autosomal dominant disease gene. Huntington's patients have movement problems, cognitive decline, and personality changes. There is no cure. There is a PCR test that can tell you if you will develop the disease. The question is, if you had a probability of inheriting the disease, would you take the test?

Some of the issues at hand include uncertainty, whether your plans would change depending on the test, financial, family, and educational planning. You may decide not to pursue that PhD or to get fetal testing or to travel the world. On the other hand, you may rather leave it up to God (or chance). You may become incredibly depressed if you have the mutation; you may be plagued with "survivor guilt" if you don't. Maybe you think ignorance is bliss; maybe you think knowledge is intrinsically valuable.

That's a lot to think about regarding a piece of knowledge for which there is no medical treatment. Thus, genetic counseling is central to those contemplating a test. But I like looking at Huntington's disease as an example of how knowledge is not inert. Just the prospect of knowledge transforms lives. This also says a lot about determinism and inevitability. The science of Huntington's disease is based on determinism. That is, the number of trinucleotide repeats in the Huntingtin gene causally determines whether (and when) someone will get the disease. Yet the disease is not seen as inevitable unless that information is known. The disease is determined by someone's genetics regardless of whether they test positive, but the patient only considers the disease inevitable if they test positive (hence the idea that not testing is "keeping hope open"). Until recently, I linked determinism with inevitability, but Dennett's Freedom Evolves that I'm reading has led me to doubt the solidity of that claim.