Equine Polysaccharide Storage Myopathy

Equine Polysaccharide Storage Myopathy (EPSM or PSSM) is a muscular disease found primarily in horses. It affects the way a horse's body metabolizes energy, leading to a variety of symptoms that can impact a horse's performance and overall health. This condition is characterized by the abnormal accumulation of glycogen and other polysaccharides in the muscles of affected horses.

Symptoms[edit | edit source]

Symptoms of EPSM can vary widely among horses but often include:

Muscle stiffness
Weakness
Reluctance to move
Muscle tremors
Sweating
Recurrent episodes of tying-up (rhabdomyolysis)

Causes[edit | edit source]

EPSM is primarily caused by a genetic mutation that affects muscle metabolism. This mutation leads to an abnormal accumulation of glycogen and related polysaccharides in the muscles. The condition is more commonly found in certain breeds, suggesting a hereditary component. Breeds commonly affected include Draft horses, Quarter Horses, and Warmbloods, among others.

Diagnosis[edit | edit source]

Diagnosis of EPSM is based on clinical signs, muscle biopsy, and genetic testing. A muscle biopsy can reveal the characteristic abnormal accumulation of polysaccharides in muscle cells. Genetic testing can identify the specific mutation associated with EPSM, particularly in breeds where the mutation has been well characterized.

Treatment[edit | edit source]

There is no cure for EPSM, but the condition can be managed with dietary changes and exercise. High-fat, low-starch diets have been shown to be beneficial in managing symptoms. Regular, gentle exercise is also recommended to help affected horses maintain muscle function and reduce the severity of symptoms.

Prevention[edit | edit source]

Since EPSM is a genetic condition, selective breeding practices can help reduce the incidence of the disease. Genetic testing of breeding stock is recommended to identify carriers of the mutation associated with EPSM.