Feline miliary dermatitis

The cat with miliary dermatitis is often frustrating for both owner and clinician, in that failure to identify the underlying cause and implement appropriate treatment can lead to frequent recurrence. Here Catherine Milley takes us through the logical process of working-up these cases.

Catherine D. Milley

BSc, DVM, Dip. ACVD - Animal Dermatology Clinic, Portland, Oregon, USA

Introduction

Miliary dermatitis is a common presentation of dermatologic disease in cats. Historically this condition was called “miliary eczema”; the word “miliary” is defined as “resembling or suggesting a small seed or many small seeds” (1), and the term found usage as it describes the feeling encountered when examining the coat of an affected cat. Lesions are often felt easier than they are seen, due to their small size and distribution within an often otherwise normalappearing coat. In more specific dermatologic terms, miliary dermatitis can be described as clusters of small, typically crusted, papules. Miliary dermatitis is not a diagnosis, but rather a reaction pattern with many different potential causes; the differential diagnoses are numerous and include hypersensitivity to flea bites; cutaneous adverse food reactions; atopic dermatitis; ectoparasites; bacterial, viral, yeast or dermatophyte infections; cutaneous adverse drug reactions; pemphigus foliaceus; dietary imbalances; feline hypereosinophilic syndrome; and urticaria pigmentosa (2). This article will review the clinical signs, typical presentation and etiologies of feline miliary dermatitis, as well as focusing on the diagnostic approach and treatment options for this common skin condition.

Clinical presentation

Miliary dermatitis can be localized or generalized, and it may be the sole presenting sign or it can occur with other primary or secondary dermatologic lesions. Most commonly, groups of small papules are found on the head and neck, limbs, trunk or dorsal lumbar region (Figure 1). Lesions that may be concurrently detected in patients with miliary dermatitis include alopecia, excoriations, erosions and ulcers. Miliary dermatitis may also be found in cats with lesions consistent with the feline eosinophilic granuloma complex (EGC) such as indolent ulcers, eosinophilic plaques and eosinophilic granulomas. Although pruritus is common in affected patients, it is not a consistent finding. This may in part be due to the discrete grooming practices of cats; owners may not visualize pruritic behavior, or may not understand what constitutes abnormal grooming behavior.

In an attempt to concisely evaluate outcome measures of therapeutics in cats affected by miliary dermatitis and various other skin lesions, a novel scale, known as SCORFAD, has been developed ( 3 ). Using this scale, 10 body regions are identified, namely the head; neck; dorsal and lateral thorax; rump and tail; flanks; sternum and axilla; abdomen; perineum; forelimbs and paws; and the hindlimbs and paws. Using this scoring system, miliary dermatitis may be classified as very mild in patients with 10 or fewer papules in one body region; mild in patients with more than 10 papules in one body region; moderate in patients with 10 or fewer papules in more than one body region; and severe in patients with more than 10 papules in more than one body region ( 3 ). [...]