This case study describes a 6 month old West Highland white terrier presenting with pruritus, erythema, lichenification, hyperpigmentation, and crusting. Skin scrapes were negative for demodex mites. Tape strips showed evidence of Malassezia. The dog was treated with antifungal shampoo and itraconazole, and placed on a hydrolyzed protein diet trial. The pruritus resolved with treatment and diet modification. While on the new diet, the condition did not relapse, suggesting an adverse food reaction or atopic dermatitis underlying the Malassezia dermatitis.

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Case study module 3
6 month old West Highland white terrier

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History and clinical
presentation
Pruritus
Erythema
Lichenification
Hyperpigmentation
Crusting

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Case work up
 List the further history needed
 List the differential diagnosis
 List the tests in order of how best to progress with the
investigations

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Questions
regarding
further history
 How long has the condition been going on
 What treatments and responses
 Diet
 Management – walking and indoor environment
 Other pets in the house?
 Is there a smell associated with the condition
 Zoonosis

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History for this case
 Fed on commercial puppy food, milk and other treats
 Walked on grass and pavement
 Indoor environment carpeted and sleeps on the owners bed
 Owners unaffected
 Owner reports a cheesy smell since the dog developed the disease
 Duration for about 6 weeks (so started at the age of about 18 weeks)
 Treated with antibiotic – cefalexin but this had no effect
 Washing with a tea tree oil shampoo bought in the pet shop

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List of differential diagnosis
 Malassezia dermatitis
 Demodicosis
 Adverse food reaction
 Atopic dermatitis
 Sarcoptic mange

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Tests in order of importance
 Skin scrapes
 Tape strip cytology
 Consider trial treatment for sarcoptic mange if high
index of suspicion
 Food trial
 Serum or intradermal allergy testing if the criteria for
atopic dermatitis are fulfilled

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Further investigations in this
case
 Skin scrapes
 Negative for demodex mites
 Tape strips
 See picture
 Trial treat for sarcoptic mange

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Questions
 How would you treat this dog?
 What steps would you take to investigate this case
further?

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Questions
 How would you treat this dog?
 Antifungal shampoo and in this case systemic antifungal – itraconazole
10mg/kg sid with food for 14 days
 Treatment until negative cytology
 What steps would you take to investigate this case further
 Maintain flea control
 Diet trial
 Finally clinical diagnosis of atopic dermatitis if pruritus persists

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Ongoing investigations and outcome
 Shampoo in 2% chlorhexidine and 2% miconazole (Malaseb; shampoo)
once a week
 Food trial with Purina Veterinary Diet a hydrolysed commercial diet for 8
weeks
 Pruritus resolved
 Relapsed when fed the original food including the milk and treats.
 The prognosis is good although the Malassezia dermatitis could recur
 Concurrent allergies to environmental allergens possible in due course

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Outcome: response to food trial and antifungal
treatment