I always wondered about his health. I've seen state photos of him sitting at the end of a ridiculously long table. People interpreted it as a power move, but it could also be because his immune system is fucked. Not a doc, but I know there's quite a few treatments that end up suppressing the immune system.
Although given the amount of people he's ordered poisoned, I'd want to keep my distance from everyone who might hold a grudge too.