They've been around for millions of years, probably date back to the dinosaurs. They developed, over time, translucent skin without any pigmentation and lost their eyes. They didn't need any of it, so eventually it was bred out of them. I think whatever these people needed would have happened in a few more generations. Whether that was pigmentation loss or something else, I don't know.
If we want to get technical, we're all a mash of mutations. The fact that we walk upright is a mutation. The way our teeth are shaped are hundreds of mutations. Fingers and fingernails. Opposable thumbs. But I'm guess you mean that you have the X-gene?