Pemphigus vulgaris in a Welsh pony stallion: case report and demonstration of antidesmoglein autoantibodies.

HYPOTHESIS/OBJECTIVES: To describe the clinical, histological and immunological findings of an equine case of pemphigus vulgaris, including the demonstration of antidesmoglein (anti-Dsg) autoantibodies. CASE REPORT: The diagnosis of pemphigus vulgaris was confirmed in a 9-year-old Welsh pony stallion with both direct and indirect immunofluorescence and immunoprecipitation studies, the latter identifying circulating anti-Dsg3 IgG. Treatment with immunosuppressive medications was initiated. Lesions were seen in the perineal area, sheath, mane, tail, eyelids, coronary bands and mucosa of the mouth and oesophagus. Initial corticosteroid treatment improved the clinical signs, but the onset of laminitis necessitated a reduction in dosage, which was associated with a recurrence of lesions and development of oral ulcers. A corneal ulcer developed after 60 days of treatment. Despite treatment with azathioprine, gold salts and dapsone, the disease progressed and the pony was euthanized. Postmortem examination showed additional lesions of the cardia of the stomach. CONCLUSIONS AND CLINICAL IMPORTANCE: Pemphigus vulgaris is rarely diagnosed in equids. We describe a case that was substantiated by the demonstration of anti-Dsg3 IgG. Response to treatment was poor, with the best response to high doses of prednisolone. Equine pemphigus vulgaris is likely to carry a poor prognosis and if there is no response to treatment, humane euthanasia is warranted.