All-white overo foals almost always die. It is unclear if this is inherent to the overo pattern, or whether it is a specific lethal gene that some but not all overos carry. This is an all-white horse, white from birth, with pink skin and brown, hazel, or blue eyes. These horses are called American White Horses and have a registry. This is caused by a lethal dominant gene.
Heterozygous horses survive and are white, but homozygous white foals die in utero.
No true albino gene has ever been discovered in horses. This is strange as albinos have been found in almost every other species. These foals cannot absorb water, for some reason, and die within a few days of birth. So the last thing a Paint breeder wants to see is an all-white foal. The lethal white that has been discussed extensively on the net is a situation that occurs in paints, particularly in Overo paints.