Behchet's Syndrome. Exactly what that entails depends on the person. In my case? Mental issues, mostly. Mild, at this point. I'm fairly cranky/reclusive/defensive without my pills, prone to falling apart completely (again, unless I have my precious crushed-beetroot sanity pills), slightly... foggy vision every once in a while, and lots of aches.
I'm told it'll get worse eventually. In 15 years I can expect to have lost most of my eyesight and have far weaker/generally crumbling bones. My sanity will likewise more or less go on vacation. In about 20 years, I probably won't be alive in any case. And it could potentially all happen sooner than that, or so I'm told by my doctor.
Oh, and I can count on having at least one cracked or broken limb at any given time, but that's more to do with being a klutz/having hilariously poor luck where getting hit by cars is concerned.
Edit: I just read this, and wow do I ever sound whiny. Sorry about that, wasn't my intent. I'm quite aware that there's much worse out there, I just have a knack for complaining about things that shouldn't get to me as much as they do.