We have it all through Mum's side of the family. My maternal grandmother had it, my uncle has it and my Mum and brother have symptoms - Mum actually was told she didn't have it but after recently developing issues with her eyes (cataracts and detached retina) she has decided to pursue genetic testing.

As wysiwyg said, there's a huge variation in presentation. My MGM didn't even know she had it - though ultimately it killed her (heart aneurysm). My uncle's presentation is very severe (severe curvature of the spine resulting in compromised lung function, elongation of hands and feet, heart issues) and he wasn't expected to live past early childhood. He is now in his late 60s and still doing amazingly. My Mum's had so few indicators that the doctors ruled it out, but it looks like she too could have it, but have had little more than eye issues developing in her 60s.

Lots of info here already but let me know if I can add anything.