I've never been diagnosed with anything, but it wouldn't surprise me if I had some form of disorder, possibly bipolar, or possibly depression. But I seem to manage just fine without any medication, so I don't worry about it.
As to if I know anyone that has been diagnosed...hahahah! Oh wow yes, my brother has been batshit crazy for decades. Ever since he was 16, he's 46 now, he was very unstable. I couldn't tell you what he is diagnosed with currently, because I don't really speak to him anymore, but I think right now they've settled on schizophrenic with a hyper-religious flavor to it. But since he was first diagnosed, and showed symptoms back in the 80's/90's, they were still trying to figure out what was what. He has spent most of his adult life in and out of jail/prison, and various mental facilities, due to his conditions.
How has it effected my life? It's effected it from top to bottom. It meant I had a brother that I looked up to, who was no longer really my brother anymore, at least not in the way I knew him to be. He was a different person, sometimes on a daily basis. It made me live in a constant state of hyper vigilance whenever he was around, as you couldn't trust him to not fly off the handle and do some very insane things. Between him threatening my life on multiple occasions, and actually trying to strangle my mother at least once, he became a stranger that I share genetic material with, and to cope with that, I had to develop a mindset that I might have to actually kill him to protect the people I love. So he stopped being a family member at all.
I got used to, growing up, getting random calls in the middle of the night, from cops, saying they picked up our brother in *insert random city in the US*, doing something crazy. We'd have to spend valuable time and money (of which we never had much) to drag his ass back here, and put him in some facility so they could try and stabilize him.
I had to deal with him developing a heavy christian subtext to his insanity, convinced that he spoke to angels and god directly.
I had to deal with the Secret Service showing up at my grandmother's house (where he lived at the time), because he'd been sending Crazy Packages to the president (George W. Bush), with random clippings from magazines, bible passages, and cuttings from old, priceless collectible books my grandmother had.
I had to deal with cleaning out his festering cess pits that were his living places, when he would get evicted.
And I currently have to deal with a guy who thinks he has been saved by his god, and yet is convinced that I'm going to burn in hell, and so he tries to act superior to me, because he's saved and I'm not.
How do I deal with it? I distance myself from pretty much all of it at this point, and live my life with the people I do actually care for, and don't communicate with the people from my past who fucked it up so much.