My dad, brothers and I all have multiple traits of it. No offical diagnosis but in terms of hyper extention, stretch marks, poor vision, long lung fields, and in one of my brothers case, his wingspan is longer than his height (by about 30cm). my dad and brothers all got their hearts tested a few years ago, as it can affect the valves.
I read up a fair bit about it so know a fair bit. I've also nursed a man who had it.
I think the big thing is heart vavles, and retina detaching are the major concerns really.