Lethal white foal syndrome

Lethal White Foal Syndrome
Courtney Doucet

Lethal white foal syndrome is a genetic defect in foals born to parents of American Paint Horse lineage. Affected foals are almost entirely white and die within days from complications due to intestinal deformities. These deformities occur because of a mutation in the endothelin receptor B (EDNRB) gene. EDNRB is known to be involved in the developmental regulation of neural crest cells that are a precursor for nerve cells and melanocytes. The types of horses that are carriers for this gene come from a lineage with the overo color pattern. Overo is specific to one of the three coat patterns common to paint horses.
Various breeding programs may be utilized by producers to hopefully ensure that a lethal foal will not be born. However, instances of lethal white syndrome have been reported by owners of other horse breeders. Clinical diagnosis includes close observations within the first few days of life as well as rectal examinations, enemas, and/or DNA testing. At this time, humane euthanasia remains the only course of treatment. Therefore, prevention of this disorder is paramount when breeding for these specific color patterns.

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