Crusting and exudation in a Welsh stallion pony Author: Mark Craig Editor: David Lloyd © European Society of Veterinary Dermatology

History -1 10-year-old Welsh pony stallion Weight 300 kg Click to reveal the text on this screen Click the forward arrow to jump to the next screen History

History -2 First signs developing over a 4-week period Papules on flank and neck, pruritus Generalised crusting and exudation Swelling of all four legs accompanied by stiffness and lameness Weight loss and lethargy No treatment by the referring vet History

Clinical signs - 1 The horse was thin and there was generalised crusting with diffuse alopecia No peripheral lymphadenopathy was detected Signs

Clinical signs - 2 Close-up views of alopecic and crusted areas Clipped area on the withers Signs

How would you approach this case? What are the next steps you would take? Make a list of your principle differential diagnoses List any samples you would collect List any tests you would perform to assist in making a definitive diagnosis Signs

Test - 1 Principle differential diagnoses Bacterial folliculitis, dermatophilosis, dermatophytosis Ectoparasitic infestation Pemphigus complex, SLE, drug eruption Allergy Differentials

Tests - 2 Tests Blood tests: routine haematology and biochemical screens; ANA test Multiple punch and excision biopsy samples from crusted and alopecic areas Skin scrapings, crusts and hair pluckings for microscopic examination, smears, bacterial and fungal culture Tests

Results Scrapings, crusts and hairs did not reveal ectoparasites or fungal structures; Dermatophilus was not demonstrated on microscopic examination Haematological and biochemical profiles were within accepted limits. The ANA test was negative Histopathology revealed a superficial pustular dermatitis. No micro-organisms were found in the lesions Tests

What now? What treatment, if any, should you now institute whilst waiting for the fungal cultures? What are now your principle differential diagnoses? Are there any other samples you would collect? Tests

Initial therapy Ectoparasitism and neoplasia were deemed unlikely Autoimmune or immune-mediated disease seemed likely and the horse was deteriorating hence therapy was initiated Prednisolone, 0.5 mg/kg daily; trimethoprim and sulphadiazine (Uniprim), 0.5 sachet daily Therapy

What is your diagnosis? What is your principle diagnosis? Do the investigations permit a definitive diagnosis? Are there any additional investigations which you think may need to be done? Therapy

Further tests Histopathology A superficial pustular dermatitis was present The pustules contained many neutrophils & acanthocytes but no micro-organisms Therapy

Diagnosis Pemphigus foliaceus Lesion type and histopathology are consistent No history of previous drug therapy Fungal culture was negative Therapy

How would you deal with this case? What is your prognosis? How will you advise the owner? What treatment would you consider? Therapy

Response to therapy - 1 After 5 days the lesions were unchanged The prednisolone dose was increased to 300 mg per day and there was a moderate improvement over a period of 10 days - decreased scaling and some hair regrowth Steroid therapy lapsed (owner’s choice) and the horse’s condition remained stable over a two-month period but then again worsened Notes

Response to therapy - 2 Prednisolone therapy at 300 mg twice daily (1 mg/kg b.i.d.) was resumed. Within 2 weeks all lesions had disappeared and after 1 month the horse was reported to be in good condition Attempts will be made to lower the dose over the coming months Notes

Prognosis Prognosis is guarded The disease may require potent immunosuppressive therapy with significant side effects It may not respond adequately Notes

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