I started manifesting symptoms when I was about eight or nine and diagnosed with hypermobility when I was fifteen. I was told: "take some paracetamol for your imaginary pain, read this pamphlet and join a ballet troupe, you lucky super-bendy person." (I may be paraphrasing slightly
) It definitely got significantly worse between about thirteen and seventeen, and I've heard that EDS tends to crop up with puberty, although now that we know more about it, my mother has noted some likely symptoms that began in my babyhood and that she just thought were normal. She and my dad are both carriers of the gene, although on my mum's side it seems to have manifested as knee and ankle weakness and my paternal great-grandmother was just considered "sickly."
I was twenty-one when I finally saw a specialist in EDS and connective tissue disorders, who joined the dots on lots of non-joint related aspects, like my autonomic issues, "cigarette-paper" scar tissue and chronic fatigue.
I was nineteen when I got my chair (I actually went to my GP to discuss it because I was struggling so badly with walking to use public transport to get to work) but once it arrived, I became completely adverse to the idea, put it in a cupboard and refused to use it until a badly dislocated knee needed nearly six months to sort itself out. After more than a decade of regular (and slowly increasing) use, I don't really think of it any differently to the splints and braces I use to support my more unstable joints during periods of activity but, man, do I hate it for cosplay!
I've found (although I accept that it's just as likely to be my own bias towards the chair and my disability and the fact that, thus far, I only really cosplay from Dragon Age, which isn't as entrenched in the public consciousness and recognisable as big franchises like Marvel) that some photographers seem to be actively put off by the chair, and I've only ever seen one wheelchair shot of one of my costumes, which unfortunately made me look like a beach ball covered in suede!
I've always found that people will talk to my husband (or whomever is pushing my chair) rather than to me, and shop assistants will happily take my card or cash but hand everything back to my attendant rather than to me, but it tends to happen more frequently in the everyday world rather than at conventions, possibly because a lot of stallholders and artists are also seated, so I'm actually at eye level.
My current WIP has long strips of scale maille on the front and back, which I've made with craft foam, so I'm still not entirely sure whether it will survive me sitting in the chair while wearing it, but at least it is a much lighter costume than my many layered Inquisitor so I'm hoping to look a bit less round in it!