Creutzfeldt-Jakob Disease (CJD), a particularly wicked form of dementia that is also (thankfully) exceedingly rare

350 cases a year in the US

I seem to remember reading somewhere that 13 people have died of it in the last 5 years, or something.

Heritable CJD? 90 cases since 1995, distributed across 5 exceedingly unfortunate families. That's according to one paper buried deep in Up-To-Date.

They don't know why it happens.

They absolutely do. A protein flips from left-handed to right-handed, and right-handed proteins dominate. It's like Olestra - it's fat, it tastes like fat, but it gives you the liquishits because you can't digest it. Or, more accurately, like Ice 9 from Vonnegut's Cat's Cradle - water is more stable in a different crystalline structure, which means it's a solid at room temperature, and the world ends. For "world" substitute "brain". It's an exponential disease because it's volumetric chemistry, not epidemiology.

They don't know the mechanisms of its operation.

Yeah it caps off the stuff normal proteins should interact with and turns living matter to inert matter. Like the Midas touch only with meat.

They don't know the mechanisms of its operation.

Yeah no it's like supersaturated fluid. Things are all good until you drop the pan and suddenly you're fudge.

Someone just starts showing signs of early stage dementia, it progresses at lightning speed (faster than any other dementia diagnosis), and they are gone in 3-5 months.

Or, "driving" to "can't sleep" to "crazy" to "in need of institutionalization" in two weeks, and "in need of institutionalization" to "no heroic measures" in another ten.

They stopped researching it, despite the fact that 1 in 2000 blood samples in the UK have bad prions in them, 'cuz two out of two researchers in France who accidentally pricked themselves with contaminated needles ended up dead.

I considered him my "extra Dad".

When I called to say goodbye I told him on speakerphone that he was one of the very few relatives I give a shit about. I have no idea who else was in the room, nor do I care.