Skins for causes of any sort probably won't go down well. You see, this is a game. People play it to have fun, and it's not so fun if the bleak world outside intrudes in such a fashion.
Also, as a high-functioning Autistic, I'd be appalled at such a skin, particularly if the spiteful eugenicists over at Autism Speaks had anything to do with it. I'm sure there are breast cancer survivors, too, who think a skin would be going too far.
Besides, how do reflect a disease or a neurological condition in an aesthetic? It's a good bit more complicated than just giving Leona pink armor, or giving Braum a bunch of smiling children.
In short, this post has something to offend nearly every demographic of League player, except, of course, the so-called "Social Justice Warriors," who are typically motivated by a need to pander to their egos in a socially acceptable manner, as opposed to belief in a cause.