Why test for PSSM1?

Polysaccharide storage myopathy is a muscle disease that can cause "tying up" symptoms: muscle weakness, shivers, work intolerance, and even muscle wasting particularly in the hindquarters.

Unlike the other inherited disorders that we test for, PSSM1 is not recessive. This means that horses which inherit the PSSM1 mutation from just one parent can show signs of this disorder. To complicate matters, not all horses with the PSSM1 mutation show signs of this disease - its effects range all the way from negligible to fatal. Not all cases of tying up are caused by PSSM1 either: one study found that only 65% of a group of horses with moderate to severe signs carried this particular mutation.

Testing for PSSM1 is valuable for both breeders and riders in eliminating or confirming a major known cause of tying up. Speak to your veterinarian about the management of PSSM1 horses.

PSSM1 in various breeds

PSSM1 has been found in:

• Quarter Horses
• Paint Horses
• Appaloosas
• Gypsy Cobs
• Belgian Drafts
• Thoroughbreds
• Warmbloods
• Polo ponies
• Connemara cross
• Belgian Draft Horses

It may also occur in other breeds and crosses.