Where do prions come from?

I read all this stuff about prion diseases, and how prions screw up normal proteins, and how they’re contagious and all but where do the prions come from in the first place? In hereditary prion diseases, I assume there’s an inherited problem with whatever makes the proteins. What about everyone else? Does it all start with one spontaneously screwed up protein, like cancer but not?

I don’t think anybody really knows enough about prions yet to say how they can be generated non-infectiously. Always got the impression that the well-known prion diseases could have been from original prions that were generated decades ago, or more.

I suspect that if there were a strictly genetic basis, prions would be much more common a problem. Maybe some kind of chemical accident in a cell, with a group of protein molecules getting exposed to an enzyme that they were never meant to, and maybe one happens to get turned into a prion, while all the other protein molecules get destroyed or half-destroyed. shrugs

I must need more coffee, I had to actually open the thread and start reading the OP before I realized that the question wasn’t, “where do prisons come from?” Going for my refill now…