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

The research article discusses a rare case of pemphigus vulgaris, an autoimmune condition, in a Welsh pony and the subsequent failure of treatment attempts, leading to the eventual euthanisation of the pony.

Clinical, Histological, and Immunological Findings

The researchers identified pemphigus vulgaris in a 9-year-old Welsh pony stallion. Several methods supported the diagnosis, including:

• Direct and indirect immunofluorescence: These are laboratory procedures used to detect the presence of specific antibodies in a sample. Direct immunofluorescence involves combining a sample from the pony with fluorescently labelled antibodies, while indirect immunofluorescence utilises a secondary fluorescently labelled antibody.
• Immunoprecipitation studies: This process involves isolating a specific protein from a complex mixture of proteins using a specific antibody. These tests identified circulating anti-Dsg3 IgG in the pony, a key indicator of pemphigus vulgaris.

Lesions were identified in the pony’s perineal area, sheath, mane, tail, eyelids, coronary bands, the mouth, and oesophagus.

Treatment and Outcome

Initial treatment with corticosteroids led to an improvement in the pony’s condition. However, the development of laminitis, a painful condition affecting the hooves, resulted in a need to reduce the corticosteroid dosage. This dosage reduction was associated with a recurrence of lesions and the development of oral ulcers. A corneal ulcer also developed after 60 days of treatment.

Despite the application of further treatments – including azathioprine (an immunosuppressive medication), gold salts (used to treat autoimmune diseases in some instances), and dapsone (a medication used to treat skin conditions) – the disease progressed. Euthanisation was the eventual decision due to the consistent progression of the disease, despite all measures.

Upon postmortem examination, the researchers found additional lesions in the cardia of the pony’s stomach.

Conclusions

The researchers concluded that pemphigus vulgaris is rarely diagnosed in horses. The disease appears to carry a poor prognosis due to the limited effectiveness of treatments, leading, in this case, to euthanisation of the pony. High doses of prednisolone (a corticosteroid) seemed to be the most effective treatment option, although this led to complications (laminitis).