Lethal White Foal Syndrome is a condition that affects some of the offspring produced by mating two overo paint horses. Several genes may be involved in teh manifestation of lethal white foal syndrome, and the mode of inheritance is not completely understood.

The condition is characterized by the failure to for certain types of nerves of the intestinal tract, resulting in failure of the intestines to move food. As the foal nurses, the milk builds up in the intestines and is unable to pass through the digestive tract. The foal colics and eventually dies. There is no suitable treatment and the condition is usually fatal within 1-5 days. Affected foals are nearly all white. Early in the embryonic development, the skin or hair pigment producing cells originate from the same tissues as cells of the developing nervous system. The lack of pigment in these foals appears to parallel the lack of nerve formation in the intestine.