While I was reading the original post and replies up until now, I was considering this "Zebra" case...
I somewhat recently saw a documentary about sleep phenomena, where this guy (not a med student, intern, resident, attending
a high school band teacher) went so long without sleep that the neurochemistry of his sleep cycle was irreversibly ****ed.
When he tried to sleep after not sleeping so long, he couldn't experience anything but the most primary stages of sleep (stage one and maybe stage two?).
His eyes would start tweaking and he'd intermittently experience wild hallucinations (involuntary R.E.M sleep), lost his job and family, and was institutionalized.
He went something like six months getting only smidgeons of R.E.M, stage one sleep, (possible) stage two sleep, and, over that time, he became more and more incoherent until he was a mute, his immune system gradually shut down, he slowly debilitated into a person-shaped failing set of organs, and then died.
I know technically deaths only directly result from cardiac/respiratory arrest, but this case (I know its real and there might be others like it) is pretty darn close to someone dying due to lack of sleep. It sounded like the WORST way to die at the time I saw the documentary too, but maybe not.
Ill try to find the original publication where this is from
I know its out there. So Ill look for that.