I don't know either, but it's a good question. I have ADHD, but I also have social anxiety, so I'm not sure what my exact issue is at this point anyway...I'd never heard of RSD.
I am VERY sensitive to anything perceived as criticism. Like I went to hold my cousin's newborn lately, and she simply said "you have to wash your hands first" and for some reason that kind of comment feels like a kick to the stomach and I don't know why. It's so stupid.
Same when homeless people (or really anyone in public) come up to me. I start panicking, afraid they're going to say or imply some tiny thing that feels like a gut punch. People keep telling me I'm overreacting, and of course I'm overreacting, but it HURTS. Honestly, I take direct, brutal insults far better.
Honestly, this extreme averse reaction to tiny or non-existent criticisms has sort of fucked my life and made me extremely avoidant.