Genes over muscle: an equine epic

By Connie Orcutt • Published: August 1st, 2017
Category: Animal Airwaves

Polysaccharide [poly-sack-a-ride] storage myopathy—or PSSM1—is a genetic muscle disease of horses. While you can’t prevent it, you can watch for signs in your equine buddy.

PSSM1 was discovered in Quarter Horses and related breeds, as well as European draft horses and warmbloods. By now, it’s been identified in over 20 different breeds.

Signs often mimic those of tying-up—that is, muscle stiffness, unwillingness to move and profuse sweating after exercise. Some horses pass urine dark with muscle pigments. The difference between tying-up and PSSM1 is that in horses with the latter, signs can appear in the absence of any exercise at all.

Most horses with PSSM1 have several bouts of muscle stiffness as training begins, but others have only one or two mild attacks each year. If you notice suggestive signs, contact your veterinarian for advice.