Malassezia Dermatitis

Introduction

Malasseszia Dermatitis is a skin disease associated with the yeast Malassezia pachydermatis. It is common in dogs but rare in cats. The yeast is found on skin and mucosal sites in healthy dogs and cats and under circumstances which remain poorly understood can proliferate and induce skin disease.

Pathogenesis

Malassezia pachydermitis proliferates and liberates enzymes and metabolites which induce cutaneous inflammation. Concurrent skin diseases such as Atopic dermatitis and primary defects of keratinisation are recognised in approximately 66% of cases. Some dogs may show hypersensitivity to Malassezia pachydermitis.

Diagnosis

History

Affected dogs usually present with a greasy skin disease often with a characteristic odour and a variable degree of pruritus. Basset hounds, Cocker Spaniels and West Highland Terriers are predisposed.

Clinical signs

Malassezia dermatitis can complicate or mimic allergic skin disease and scaling skin disorders. The main clinical signs are erythema and a greasy exudate which may result in matted hair with variable amounts of alopecia and scaling. Hyperpigmentation and lichenification occur in chronic cases. Concurrent erythematous otitis externa with variable ceruminous discharge is common. The degree of pruritus is variable but can be extreme especially on the face in a small number of dogs.

References

• • Regional lesions: muzzle, ears, interdigital, perianal
  • Or generalised disease
  • Erythematous, hyperpigmented, lichenified and scaly lesions with alopecia
• Microscopically:
  • hyperkeratosis, parakeratosis
  • Spongiotic pustular dermatitis
  • Acanthosis
  • Organisms are usually present, minimum 3-5 yeasts per high-power field must be found to imply cause of disease

Grossly, regional lesions may be seen around the muzzle, ears, interdigital, and perianal. Other common signs include erythema, hyperpigmentation, lichenified and scaly lesions with alopecia.

Microscopically, one may see;hyperkeratosis, parakeratosis, spongiotic pustular dermatitis, Acanthosis.