PSSM2 – Navigating the Path to Diagnosis and Management

PSSM2 is not something that any horse owner wants to have as a diagnosis for their horse’s behavioral and physical problems, but it is prevalent enough that we need to make sure we are sufficiently educated on the symptoms and options for diagnosing and managing.

What Is PSSM2?

Polysaccharide Storage Myopathy (PSSM) is a glycogen storage disorder that affects skeletal muscles in horses. PSSM2, a specific subtype, is characterized by abnormal glycogen metabolism, leading to the accumulation of abnormal polysaccharides in muscle cells. While the exact cause of PSSM2 remains elusive, it is believed to have a genetic basis, with certain breeds being predisposed, including Quarter Horses, Paint Horses, and Warmbloods.

It is always important to be aware of our horse’s behavior – it is, after all, the only way they can communicate with us.

What is “normal” vs “abnormal” behavior for a horse that is comfortable vs uncomfortable?

Unwanted behaviors from a human perspective can include pinning ears, pawing, bucking, rearing and other manifestations of a horse’s pain, discomfort, anxiety or confusion.

Finding the underlying cause can be challenging, including evaluating for PSSM.

Symptoms of PSSM2:

While there may be multiple reasons for behavioral changes, recognizing the signs of PSSM2 is crucial for early intervention and management. The symptoms may vary in severity and can manifest as:

  1. Stiffness and discomfort: Affected horses may exhibit stiffness, especially during exercise or after periods of rest. They may appear reluctant to move or exhibit discomfort when asked to perform certain movements.
  2. Exercise intolerance: Horses with PSSM2 may demonstrate a reduced tolerance for exercise, showing signs of fatigue or unwillingness to engage in physical activity.
  3. Muscle atrophy: Chronic cases of PSSM2 can lead to muscle wasting or atrophy, resulting in a decreased muscle mass, particularly along the topline and hindquarters.
  4. Sweating excessively: Some horses may sweat excessively, even during mild exertion, which can be indicative of muscle discomfort or pain.
  5. Tying-up episodes: Severe cases of PSSM2 may culminate in episodes of tying-up, where the muscles become rigid and painful due to exertion or stress.
In Part Two we will dive into what we know, what we don’t know and the routes to diagnosis and management.

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