LWO stands for Lethal White Overo, also known as Lethal White Foal Syndrome (LWFS) or Overo Lethal White Syndrome (OLWS) - it is a recessive disease
LWO is another disease associate with Pattern - in this case the Frame Overo patterning gene. Foals affected by Lethal White Overo dies shortly after birth due to intestinal blockage. Their coat color is entirely white. There is no effective treatment.
OLWS is found in any breed where the paint overo pattern is found such as Quarter Horses, Paints, Miniature Horses, and Thoroughbreds.