FieldDxPurpura Hemorrhagica MyopathyClinical signs, differential diagnosis, treatment and prevention in horses.
Overview
An immune-mediated vasculitis of horses, most often appearing 1-2 weeks after apparent recovery from strangles. A type III hypersensitivity reaction: antibody-antigen immune complexes (commonly against Streptococcus equi subsp. equi cell wall protein) deposit in small blood vessel walls.
Clinical signs
- Usually 2-4 weeks after respiratory infection.
- Acute-onset muscle pain, swelling, abnormal gait, plus signs of purpura hemorrhagica.
- High case-fatality rate.
- Increased serum activity of muscle-derived enzymes.
- Muscle biopsy confirms infarction.
Predisposing factors
- Sequela to Purpura hemorrhagica.
Look-alikes to rule out
Equine Infectious Anemia (EIA) Equine Infectious Anemia (EIA / Swamp Fever) Equine Viral Arteritis
Treatment
- Treatment of purpura hemorrhagica.
- Supportive.
- Pain relief.
Prevention
Prevention of respiratory disease.
Source
A Textbook of the Diseases of Cattle, Horses, Sheep, Pigs and Goat by ELSEVIER (Page 1385 / Table 15-2)
A Textbook of the Diseases of Cattle, Horses, Sheep, Pigs and Goat by ELSEVIER — Purpura Hemorrhagica
MSD Veterinary Manual — Purpura Hemorrhagica (accessed 2026-08-11)
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