Polysaccharide Storage Myopathy is a genetic muscle condition causing recurrent painful episodes in affected horses. Dietary and exercise management dramatically improves welfare outcomes.
PSSM causes significant, recurrent suffering in affected horses — episodes involve genuine muscle pain that can be severe enough to cause the horse to refuse movement or show distress behaviors. Historically, many horses were repeatedly diagnosed with tying-up without identifying the underlying genetic cause, leading to repeated painful episodes without targeted management. Genetic testing now allows definitive diagnosis and targeted dietary intervention. The high-fat, low-starch diet required for PSSM management, combined with consistent daily exercise, dramatically reduces episode frequency and severity. Welfare monitoring should include regular assessment of episode frequency, exercise tolerance, and behavioral indicators of muscle comfort. Properly managed PSSM horses can have excellent quality of life.