It isn't as unusual as you think - I believe this is the condition that Michael Jackson has. It does also effect caucasion people - I have a few small spots that I've been told may be this. Basically, from what I have been told these areas will not "tan" when you are exposed to the sun. It is also a reminder that one should use a good sunscreen. Beyond that I would consult with a dermatologist. I am sure that the worst of this is your daughters age as becoming a teen is difficult enough without something to draw negative attention to about one's physical appearance. I have a very prominent "wine stain" birthmark on my right wrist and up my arm. I am in my 40s so I am totally oblivious to it most of the time but I know when I was younger children and teens often commented or questioned about it. If your daughter is very self-conscious about it there is a make-up that can be used to cover birthmarks that could probably also blend the white spots away. I do not recall the name but I'm sure it will come up on a google search - it has been around for decades. Best of luck.