Need Some Help

So I need some writing help. I'm currently developing a story with a young person who when born was mistaken for male up until puberty. When puberty hit, they started to develop like a young woman and not a man. I'm wondering if there is a specific medical condition that can describe that. I don't really want to create one for this story because it just won't feel accurate to me. I want it to feel real and plausible. Any help would greatly be appreciated :).