Polysaccharide storage myopathy 1 (PSSM1)
PSSM1 is one of the 5 tests in the 5-panel. The 5-panel is relevant to Quarter Horses, Paints, Appaloosas, Quarter Ponies and any other breeds with some Quarter Horse bloodlines.
PSSM1 is also common in Gypsy horses and some heavy horse breeds. It is also found (but rarely) in various riding horse breeds.
PSSM is a muscle disease that can cause "tying up" symptoms: muscle weakness, shivers, work intolerance, and even muscle wasting.
Unlike most 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 undetectable to fatal.
Gene or region and technical reference
Gene: GYS1 (causative). Reference: McCue et al. (2008)
n. Test developed using manufactured DNA, animal controls.
PS1. Test developed using manufactured DNA, animal cases.