Affected gene: EDNRB
 Inheritance: Autosomal recessive, in horses with the Overo coat color.
 Mutation: EquCab3.0 g.50503041_50503042delinsCT.,
Important
The frame overo pattern is the one associated with the risk of lethal megacolon (LWFS) when a foal is homozygous for the EDNRB mutation.
 Sabino and splash white patterns are not associated with LWFS.
A horse may appear to be “simply piebald” without the specific overo type being visually obvious.