We talked about that sad group of people who make their disease their identity.
Pretty much any Single Issue Wonk. Only really has one subject they can talk about, my little sister went through that. The only conversation she could have was about TGIF (The Friday lineup of shows on some station'rother.) Or sports, or "I'm Bisexual!"
Yes, we know. My nephew knew he wanted to be a Herpetologist when he outgrew the Dinosaur book he got when he was 7. He's like 15 now, and he can also talk about girls.
My point is, it's kinda nice, knowing that guy, who knows so much about cars, when you can't tell which belt is making that noise when you break hard, because you're driving, with the hood down.
Doesn't mean you want to hang out with him, all the time. Chronic diseases are complicated, involved and tend to dominate your life. (I have Fibro, but if you ask me, I'm a Science Fiction writer.) I don't really resent people who focus on it so much.