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Compendium April 2012 (Vol 34, No 4)

Clinical Snapshot: A Poodle With a Facial Lesion

by Anne Fawcett, BA (Hons), BSc(Vet) (Hons), BVSc (Hons), CMAVA, Angela Phillips, BVSc, MVS, MACVSc

    Case Presentation

    A 4-year-old, neutered miniature poodle presented with a suspected dog bite to the muzzle. The poodle had been playing outside with another dog in the household when the lesion suddenly appeared. At presentation, 24 hours after the appearance of the initial lesion, multiple pruritic, papular, pustular, and ulcerative lesions were present on the bridge of the muzzle (FIGURE A and FIGURE B). Significant crusting was also present. The dog was otherwise well, with no history of systemic disease and no recent administration of medication. There was no evidence to support or exclude an insect bite or exposure to a contact irritant.

    The owners declined a diagnostic work-up; therefore, the dog was treated empirically with amoxicillin–clavulanic acid (12.5 mg/kg PO q12h) and hydrocortisone aceponate cutaneous spray (1.52 µg/cm2 q24h). The dog presented again 48 hours later for the appearance of similar lesions involving the margins of the pinnae.

    1. What are the diagnostic differentials for this lesion?

    2. What diagnostic tests should be performed, and in what order?

    Answers and Explanations

    1. Diagnostic differentials include eosinophilic folliculitis and furunculosis secondary to acute hypersensitivity to insect envenomation, ectoparasites (e.g., Demodex mites, Sarcoptes scabei), dermatitis secondary to exposure to a contact irritant, immune-mediated disease (pemphigus foliaceus, pemphigus erythematosus), dermatophytosis, sterile eosinophilic pustulosis, and subcorneal pustular dermatosis. Neoplasia (e.g., mycosis fungoides, mast cell tumor, squamous cell carcinoma) was considered unlikely given the acute onset of lesions and the age of the dog. Drug eruption was considered unlikely given a lack of known exposure to medication.Solar dermatitis was considered unlikely based on the clinical presentation.

    2. The diagnostic tests used should start with the most cost effective and least invasive. In this case, examination of the lesion under a Wood lamp produced negative results, although this finding does not rule out dermatophytosis. Superficial and deep skin scrapes were negative for mites. Impression smears were negative for fungal elements and ectoparasites; however, a population of mixed inflammatory cells (mostly neutrophils and eosinophils) was seen. Neutrophilic inflammation is commonly superficial and secondary, particularly in association with excoriation or ulceration of the skin. A large number of eosinophils may reflect an allergic, parasitic, or (less commonly) neoplastic lesion such as a mast cell tumor. Mast cells were not identified on cytologic evaluation. A punch biopsy of the lesion was performed with the patient under general anesthesia, revealing a severe perifollicular inflammatory reaction consisting mainly of eosinophils with fewer macrophages, lymphocytes, and neutrophils in the dermis. Some hair follicles were ruptured, with numerous eosinophils surrounding free hair shafts. The biopsy confirmed ulceration of the epidermis with superficial accumulation of suppurative inflammatory exudate. Fungal culture of the lesion was negative.

    ***

    A diagnosis of facial eosinophilic furunculosis secondary to insect envenomation was made on the basis of the anatomic location of the lesion and histopathology results. Facial eosinophilic furunculosis is an acute condition, predominantly of the nose and muzzle, characterized by papules, pustules, excoriations, and ulceration. It is classically associated with venomous insects, but some cases are associated with drug administration.1 Lesions may also appear on the trunk, extremities, and lips.2,3 In this case, the lesions on the pinnae were thought to be due to reexposure.

    Most affected dogs are otherwise well; however, some may present with pyrexia, lethargy, or reduced appetite.2,3 The condition may be self-limiting2; however, systemic glucocorticoids are generally required at a dose of 1 to 2.2 mg/kg.1,3 Monotherapy with systemic glucocorticoids is generally adequate, whereas monotherapy with an antimicrobial agent is unlikely to hasten clinical resolution.3

    In this case, the previously prescribed antimicrobial therapy was maintained for the duration of its course, and the topical glucocorticoid was discontinued in favor of systemic therapy (prednisolone, 1 mg/kg PO bid for 10 days, then tapered off). Within 1 week, the lesion was no longer pruritic, and within 2 weeks, it had reduced in size by 50%. It was almost completely resolved within 3 weeks. The owners were advised to keep the dog indoors to limit exposure to venomous insects.

    References

    1. Mauldin EA, Palmeiro BS, Goldschmidt MH, Morris DO. Comparison of clinical history and dermatologic findings in 29 dogs with severe eosinophilic dermatitis: a retrospective analysis. Vet Dermatol 2006;17:338-347.

    2. Scott DW, Miller WH, Griffin CE. Skin immune system and allergic skin diseases. In: Muller & Kirk’s Small Animal Dermatology. 6th ed. Philadelphia: WB Saunders; 2001:543-666.

    3. Curtis CF, Bond R, Blunden AS, et al. Canine eosinophilic folliculitis and furunculosis in three cases. J Small Animal Pract 1995;36:119-123.

    NEXT: Clinical Snapshot: Lethargy, Fever, and Anorexia in a Thoroughbred Weanling

    didyouknow

    Did you know... Allergy testing is only useful after atopic dermatitis has been diagnosed because patients suffering from other pruritic diseases may have positive results on these tests, as may healthy dogs.Read More

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