EPSM in various breeds--an abstract

["guest@endurance.net" <guest@endurance.net>]

CMNewell, DVM reshan@deyr.ultranet.com
Polysaccharide storage myopathy in Morgan, Arabian, and Standardbred related horses and
Welsh-cross ponies.
Vet Pathol 37[2]:193-6 2000 Mar
Valentine BA, McDonough SP, Chang YF, Vonderchek AJ

Polysaccharide storage myopathy is an equine neuromuscular disorder 
characterized by accumulation of glycogen-related polysaccharide
inclusions within skeletal muscle fibers. The pathologic criteria
 for diagnosis of this disorder are somewhat controversial; however,
periodic acid-Schiff-positive, amylase-resistant inclusions are 
considered pathognomonic. Although these inclusions are most often
found in affected horses related to the Quarter Horse, draft horse, 
and Warmblood breeds, this report describes these characteristic
inclusions in muscle of five horses from nonrelated breeds (two Morgans,
 one Arabian, one Arabian x Thoroughbred, and one
Standardbred) and two Welsh cross ponies. Affected horses had 
histories of recurrent exertional rhabdomyolysis, and one developed
progressive weakness leading to increased recumbency. The affected 
ponies were part of an unrelated research project and had no
apparent clinical signs.