Lethal White Syndrome in Horses?

I've had and been around horses all my life and someone told me something I had never heard of before. I have miniature horses and a few of them have blue eyes. A mare with 2 blue eyes recently had a filly with 2 blue eyes. My boyfriends aunt supposedly knows alot about horses as well and she said if you breed a blue eyed stallion with a blue eyed mare there baby would die from lethal white syndrome because the blue eyes carry that bad gene. I had never heard of this and did some looking up and found the lethal white syndrome could occur in any paint horse horse, not just the ones with blue eyes. So does anyone know more about this?