Spontaneous bilateral superficial digital flexor tendon rupture in a horse with guttural pouch empyema and suspected purpura hemorrhagica

Abstract

Summary Case history An 11‐year‐old Quarter Horse gelding was evaluated for urticaria, generalised discomfort, distal limb oedema, spontaneous dropped fetlocks, and progressive hindlimb lameness. Prior infection status with Streptococcus equi subspecies equi was unknown. Clinical findings The horse had bilateral hindlimb oedema, generalised wheals, progressive hindlimb lameness, and dropped fetlocks of the right and left hindlimbs. The horse was intermittently pyrexic and was ultimately subjected to euthanasia due to deteriorating clinical status. Diagnosis Suspected purpura hemorrhagica associated with leukocytoclastic vasculitis of the superficial digital flexor tendons and spontaneous tendon rupture. Treatment and outcome The horse was treated with a combination of antibiotic therapy (enrofloxacin and penicillin), nonsteroidal anti‐inflammatory drugs (phenylbutazone) and corticosteroids (dexamethasone), with no improvement in clinical status. The horse was subjected to euthanasia due to poor prognosis and unfavourable response to therapy. Post‐mortem examination revealed unilateral guttural pouch empyema, multifocal cutaneous infarction and bilateral rupture of the superficial digital flexor tendons. Streptococcus equi subspecies equi was isolated in pure culture from the guttural pouch. Microscopically, leukocytoclastic vasculitis typical of purpura hemorrhagica was documented in the skin. Unexpectedly, similar vasculitis was also observed in the superficial digital flexor tendons. Clinical relevance This report documents the first equine case of suspected purpura hemorrhagica associated with leukocytoclastic vasculitis of the superficial digital flexor tendons and spontaneous tendon rupture. Spontaneous tendon rupture should be considered a potential sequela to infection with Streptococcus equi subspecies equi in horses due to immune‐mediated vasculitis.