07/07/2026
🐴 Muscle twitching, weakness or sudden collapse in horses? It could be genetic.
Hyperkalemic Periodic Paralysis (HYPP) is an inherited muscle disorder caused by a mutation in the SCN4A gene. Affected horses may experience episodes of muscle twitching, weakness, prolapse of the third eyelid, or, in severe cases, collapse.
HYPP is most commonly seen in American Quarter Horses, but it can also occur in American Paint Horses, Appaloosas, and other breeds with Quarter Horse bloodlines.
A simple DNA test can identify whether a horse carries the HYPP mutation, providing valuable information for owners and breeders. Genetic testing supports informed breeding decisions and helps reduce the prevalence of this inherited condition in future generations.