Malassezia dermatitis

7 Malassezia dermatitis

INITIAL PRESENTATION

Pruritus with crusting, lichenification, erythema and alopecia.

INTRODUCTION

Malassezia pachydermatis is recognized as one of the major flare factors contributing to pruritus, especially in atopic dogs. Several different Malassezia species have been isolated but, of these, Malassezia pachydermatis, a non-lipid-dependent species, is the most studied in veterinary medicine. Malassezia pachydermatis is considered to be commensal on canine and feline skin, and can cause infections when the microclimate on the skin surface or in the ear is altered, or if the host immune responses are compromised. The lipid-dependent species M. sympodialis and M. globosa have been isolated from cats. The recognition of Malassezia dermatitis and its appropriate treatment was the key to successful management of atopic dermatitis in this case.

CASE PRESENTING SIGNS

An atopic 2-year-old castrated West Highland white terrier was re-presented with a history of recent pruritus, lichenification, hyperpigmentation and erythema affecting the axillae, extensor aspects of the elbows, and the groin.

CASE HISTORY

In most cases Malassezia dermatitis is associated with an underlying hypersensitivity disorder and the distribution of clinical signs may give an indication of the underlying condition. The relevant history to this case included:

• A diagnosis of atopic dermatitis had been made 1 year previously and was based on history, clinical signs, failure of response to an appropriate diet trial and intradermal reactivity to environmental allergens (house dust mites, storage mites and mould allergens).

• Response to allergen-specific immunotherapy was poor but remission of pruritus had been successfully achieved with ciclosporin (5 mg/kg on alternate days).

• There was no change in management or treatment before the flare-up.

• There had been a recent flare-up of pruritus that had coincided with very warm and humid weather.

• The flare-up had a duration of about 3 weeks, which did not coincide with the animal’s regular visits to a grooming parlour.

• Good flea control was maintained with monthly applications of a spot-on fipronil and s-methoprene.

CLINICAL SIGNS

In dogs, the clinical signs of Malassezia dermatitis vary according to the intensity of the infection and the area affected. Infection can cause localized or generalized disease and pruritus is a common presenting sign. In most cases the skin lesions include erythema, scaling, hyperpigmentation, lichenification and crusting. Individual, or several concurrent sites such as ears, lips, muzzle, ventral neck, axillae, ventrum, perianal and feet may be involved. Dark brown waxy exudate in the ear canals or adherent to the nails is suggestive of Malassezia infection. Frequently, peripheral lymphadenopathy is also present.

Malassezia dermatitis is less common in cats. It has been associated with facial dermatitis and with otitis externa secondary to allergic skin disease. Generalized lesions in cats have been associated with immunedysregulation in conditions such as the paraneoplastic syndromes.

In this case, the clinical signs included:

• Reactive lymphadenopathy of the pre-scapular and popliteal lymph nodes.

• Hyperpigmentation, lichenification, crusting and erythema on the axilla and the anterior aspects of the elbows (Fig. 7.1).

• Convex aspects of both ear pinnae and vertical ear canals were erythematous and oedematous (Fig. 7.2).

• Otic examination revealed erythematous-ceruminous otitis externa.

• The tympanic membranes were visible once the exudate had been flushed out using an ear cleaner.

Figure 7.1 Erythema, hyperpigmentation and lichenification in the axilla.

Figure 7.2 Erythema and yellowish waxy exudate in the ear.

Tags: Saunders Solutions in Veterinary Practice Small Animal Dermatolo

Sep 3, 2016 | Posted by admin in SMALL ANIMAL | Comments Off

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