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

2. History -1 10-year-old Welsh pony stallion Weight 300 kg
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History

3. 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

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

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

6. 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

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

8. 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

9. 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

10. 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

11. 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

12. 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

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

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

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

16. 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

17. 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

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

19. Review
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Notes