Adjacency, or What to Say?

More often than not, people that I meet don’t really have any idea what SCA-3 (spinocerebellar ataxia type 3) is; strangers can see immediately that I move slowly, that I am unsteady and uncoordinated. To those that have asked, I have sometimes said that SCA-3 is “ALS-adjacent.” The more that I learn about ALS, the more I think I might need a better shorthand, because for all the similarities in the conditions, there are some stark differences, starting with this one: ALS is 100% fatal. However, relatively few people die because of SCA: many die with the disease, but not of it. (For example, some people may aspirate their food because of difficulties swallowing (related to SCA-3) and they may subsequently die of pneumonia.)

Whereas I know where my SCA-3 came from — thanks, Dad, you couldn’t have just given me your bad sense of humor and a drinking problem! — a small fraction of ALS cases are linked to genetic markers (less than 10%); most are random. In cases of ALS that are genetic, ALS is autosomal dominant, as is SCA-3. That means that the genetic mutations that signal it are on autosomes (non-sex chromosomes), and that only one mutated copy of the gene is needed to cause the disorder (dominant). However, SCA-3 has what is known as high (complete) penetrance. Basically, this means that every person who has the mutated gene (50% of children of those with mutated gene) will develop symptoms over a “normal” lifespan. With ALS, penetrance is incomplete in family cases — not everyone with the mutated gene develops the disease. But, again, most cases are not genetic. Both conditions demonstrate age-dependent penetrance, meaning that for carriers, the probability of developing symptoms increases with age. Finally, the prognosis differs with age of onset: for SCA-3, age at first symptoms is linked to the severity of the condition; the younger one shows symptoms, the more severe will be the case. The opposite is true for ALS. One reason that Stephen Hawking lived as long as he did is that he developed symptoms at a fairly early age — though he was an outlier even taking this into account.

I recently started taking part in a drug “experiment” in which I am given a modification of a drug formerly approved only for use with ALS patients — until the drug maker hears back from the FDA about their request to market it for use with SCA patients. There is that little piece of validation of my shorthand explanation of SCA-3. But there is a kind of halo-effect or cultural gravitas around ALS — maybe in part because it is linked to Lou Gehrig or Stephen Hawking — but likely more due to the randomness and severity of it all. Maybe part of being raised Catholic is that I still view suffering as a badge of honor, and so there is still the stolen valor quality of the “ALS adjacent” even as a quick explanatory handle for SCA-3. I can always say more if given the chance, or point them here. Or just use my favorite explanation for days when things aren’t going my way: everything hurts, and nothing works.