Sometimes the worst nightmares are the ones you don’t have. There are numerous conditions, disorders, and illnesses that either limit or prevents the amount of sleep an individual is able to get. Many of them are quite dangerous, but none of them are as frightening or rare as fatal familial insomnia.
Source: The People Who Can’t Sleep
I think a significant correction needs to be made to this article. The disease is not caused by the PRNP gene by itself, and the PRNP gene is not what accumulates in the brain. It is the product of the PRNP gene, the protein that it produces, that causes the problem, and only when it produces a variant form of the protein.
Prion diseases, at their heart, are caused by misfolded forms of normal proteins in the nervous system. These messed up proteins accumulate, causing a variety of injuries to neurons and we do not know all the mechanisms by which this happens.
The thing that makes prion diseases nasty is that the misfolded proteins can interact with normally formed proteins, and convert them into the bad kind. This is how the diseases can be transmissible. Think about it: if you just had a genetic disease that gave you this screwed up protein that eats holes in your brain, that’s terrible, but you can’t pass it on to anyone except your kids. However, some prion diseases are transmissible because another animal (or person) can get the bad proteins into their system (through eating them), and that can set off a chain reaction that starts the disease in their brain, even if they don’t have a mutation. What’s more, we don’t know for sure how much this can spread between species.
Mad Cow Disease spreads in herds because some of the various protein additives that went into cows’ feed were made of other dead cows, some of which probably died of the disease. Those cows’ nervous tissues end up in the food supply, and there you have it. The human example is Kuru, which spread through natives in Papua New Guinea who had a ritual of cannibalizing their dead. They also called it “laughing disease” because the involuntary shaking it caused looked like fits of laughter.