Track: Case Reports

Abstract:

Zoonotic dermatophytosis is common, yet its histopathologic overlap with psoriasiform dermatitis is rarely highlighted. We present a case of kitten-associated fungal exposure followed by corticosteroid treatment, resulting in an eruption with features of both dermatophytic folliculitis and guttate psoriasis. A 17-year-old female developed a pruritic cutaneous eruption shortly after adopting a kitten that had a small alopecic lesion. Clinical examination revealed pustules evolving into annular erythematous papules and plaques with central clearing as well as overlying white scale on the extremities, trunk, and genitals, sparing the palms and soles. Systemic and topical corticosteroids worsened the eruption. A brief febrile illness preceded rash onset. Strep testing was negative. On punch biopsy, the epidermis showed spongiosis, parakeratosis, and neutrophil-rich intracorneal serum collections. Although this pattern is not classic for guttate psoriasis, eczematous changes are recognized in several non-classic variants. PAS and GMS stains additionally demonstrated folliculocentric fungal involvement, with hyphae and yeast forms in hair shafts. However, fungal elements were absent from the stratum corneum and epidermal surface. Given the history of kitten exposure, subsequent corticosteroid treatment, and widespread annular lesions, this eruption may represent a pure dermatophytic folliculitis resulting from cat exposure. However, we cannot rule out that this dermatophyte infection may have also acted as a trigger for a guttate psoriasiform eruption in a predisposed host. This case underscores the diagnostic ambiguity at the interface of dermatophyte infection and psoriasis and illustrates the importance of clinicopathologic correlation and awareness of infectious triggers when evaluating atypical psoriasiform dermatitis.

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Jacqueline Kunesh