Polysaccharide Storage Myopathy (PSSM) is a group of hereditary muscle disorders affecting horses, leading to abnormal accumulations of glycogen and other sugar molecules in the muscles. This condition can impact various breeds and is particularly common among draft horses, Quarter Horses, and Warmbloods. If left unaddressed, PSSM can severely impact a horse’s quality of life and athletic potential. With proper management and care, however, many horses with PSSM can live comfortable and active lives. Here’s what you need to know about this condition, including its symptoms, diagnosis, and treatment options.
What is PSSM?
PSSM is a genetic condition that results in an abnormal storage of polysaccharides, specifically glycogen, and other sugar molecules, in a horse’s muscles. This excess sugar disrupts normal muscle function, leading to muscle stiffness, cramping, and, in severe cases, muscle damage.
PSSM Type 1
This type is due to a genetic mutation in the GYS1 gene, which controls glycogen synthesis. Horses with this mutation produce excessive glycogen, leading to muscle issues. Type 1 can be diagnosed through genetic testing.
PSSM Type 2
The exact cause of Type 2 PSSM is less understood, and there is no definitive genetic test for it. However, horses diagnosed with Type 2 show similar symptoms to those with Type 1. Diagnosis often relies on muscle biopsy results, where the abnormal glycogen accumulation can be observed microscopically.
The prevalence of PSSM varies among breeds, but it’s especially common in horses bred for their power and muscle mass, such as draft breeds and some Quarter Horses. Horses with PSSM may experience symptoms from an early age, but signs can also manifest or worsen with intense physical training or dietary changes.
Symptoms of PSSM
Horses with PSSM may show a range of symptoms, which often worsen with exercise or after periods of rest. Common signs to look out for include:
Muscle Stiffness and Pain
Horses with PSSM often display stiffness, particularly in the hindquarters. This may resemble tying-up episodes, where horses develop hard, painful muscles during or after exercise.
Reluctance to Move
Due to muscle discomfort, affected horses may resist moving forward, refuse to turn, or even stand still for prolonged periods.
Sweating and Shaking
Horses experiencing a PSSM flare-up may sweat profusely, even with minimal physical exertion, and may visibly tremble or shake.
Muscle Atrophy
In chronic cases, PSSM can lead to muscle wasting over time, as repeated muscle damage can reduce muscle mass and tone.
Weakness and Poor Performance
Horses with PSSM may appear weak and tire easily, struggling to perform tasks that are otherwise manageable for their breed and age.
The symptoms of PSSM can vary widely, and some horses may only exhibit mild signs. However, the discomfort these symptoms cause should be addressed as they can lead to behavioral changes and affect a horse’s overall well-being. Consulting with an experienced equine hospital can provide a clear diagnosis and help devise a treatment plan tailored to the horse’s needs.
Treatment of PSSM
While there is no cure for PSSM, appropriate management and treatment can significantly improve the quality of life for affected horses. Key treatment strategies include:
Dietary Adjustments
Since PSSM involves abnormal sugar storage, diet plays a crucial role in management. A low-sugar, high-fat diet is often recommended to reduce glycogen storage in the muscles. Forage-based diets that limit grains and other carbohydrate-rich feeds can be beneficial. Adding a fat supplement like vegetable oil or a specialized high-fat feed can provide the necessary calories without adding carbohydrates.
Regular Exercise
Exercise helps mobilize glycogen stores and prevents muscle stiffness. Horses with PSSM benefit from consistent, low-impact exercise routines, such as daily turnout and controlled rides that minimize intense exertion.
Veterinary Monitoring
Working with a knowledgeable equine hospital, like Signature Equine Hospital, allows for proper diagnosis, periodic muscle enzyme testing, and ongoing assessment of treatment efficacy. Regular veterinary check-ups ensure that the horse’s health is monitored and any necessary adjustments to diet or exercise plans are made.
Medication
In some cases, veterinarians may recommend specific medications or supplements to alleviate muscle pain and improve metabolic processes within the muscle. These medications are typically used on a case-by-case basis and tailored to the individual horse’s needs.
Effective management requires a holistic approach that combines nutrition, consistent exercise, and close monitoring to prevent painful flare-ups and maintain muscle health.
Let Signature Equine Hospital Help
Polysaccharide Storage Myopathy, or PSSM, poses challenges for both horses and their owners. With early diagnosis and a carefully crafted treatment plan, many horses can manage the symptoms effectively and continue to live active lives. Recognizing the signs of PSSM early and seeking professional guidance from an equine hospital can make all the difference.
If you suspect your horse may be affected by PSSM or would like to learn more about managing this condition, contact Signature Equine Hospital today. Our team of experts is dedicated to providing compassionate and personalized care for every horse.