Dr. Carol McLeod called yesterday afternoon to say yes, just as we'd suspected, Jewell's muscle enzyme levels were high.
We discussed options, and we decided on the less-invasive hair follicle test for determining if Jewell is positive for genetically induced PSSM. Dr. McLeod visited the University of Minnesota Web site to download the papers and instructions on submitting the hair sample.
In the meantime Stephanie Valberg, DVM, PhD, Dipl. ACVIM, of the University of Minnesota Equine Center, responded to my questions about Jewell and PSSM.
Quite a bit of information on PSSM can be found on the University of Minnesota Web site as well as on TheHorse.com by searching under polysaccharide storage myopathy
"Basically there are many reasons why horses can tie up," said Valberg in her personal correspondence. "For Quarter Horses, 10% have the GYS1 genetic mutation for PSSM, so (the genetic test) is a good place to start. If that is negative and serum vitamin E is normal, then a muscle biopsy helps to look for other causes of tying-up."
There is a good flow chart for determining which test(s) is/are needed (based on your horse's breed) in the article The Gene for PSSM Has Now Been Identified! on the University of Minnesota Web site.
"Polysaccharide storage myopathy (PSSM) is a common form of tying-up in many horse breeds and is characterized by excessive and abnormal storage of sugar (polysaccharide) in muscle cells," the article stated. "We have recently found a mutation in a gene that is highly associated with the presence of abnormal polysaccharide in muscle biopsies in several horse breeds. The genetic test for this mutation is now commercially available to horse owners and veterinarians through the University of Minnesota Veterinary Diagnostic Laboratory. We are calling this the classic or type 1 form of PSSM. This mutation is accounts for greater than 90% of PSSM cases in some horse breeds. This mutation appears to have its origins prior to the foundation of modern horse breeds, which is why it occurs in several horse breeds." The article "Glycogen synthase (GYS1) mutation causes a novel skeletal muscle glycogenosis" was authored by McCue M.E.; Valberg, S.J.; Miller, M.B.; Wade, C.; DiMauro, S.; Akmand, H.O.; Mickelson, J.R.
There is also a Frequently Asked Questions page about PSSM at the University of Minnesota Web site.
Dr. Valberg also recommended I go back to Dr. Joe Pagan, founder of Kentucky Equine Research, and ask him about the pasture grasses and get specific recommendations from him as an equine nutritionist on feeding, including grazing and hay.
Still looking for your experiences with PSSM horses. Several have sent me personal correspondences about their PSSM horses and how well they did with proper managment!
