I don't know how old I was when it started, but I had some other major health issues since early childhood, requiring numerous hospitalizations, so it's hard to say. It was finally diagnosed when I was in my mid-20s, and they were trying to figure out why the repetitive pain I had in my wrists was NOT carpal tunnel, which is so clearly should have been. Because what else is there? Sigh. Turns out all the other random pain I had various places in my body were related, imagine that!