Bullous Tinea: Single-Center Retrospective Histopathologic Review of 25 Skin Biopsies.

Bullous dermatophytosis is a rare blistering disorder resulting from fungal infection. Limited literature describes the clinical and microscopic features of this disease. To summarize the histopathologic and clinical features of 25 biopsy-proven cases of bullous tinea. The study was a single-center retrospective review of patients diagnosed with bullous dermatophyte infection by skin biopsy. Bullous tinea is rarely suspected clinically in biopsy-proven cases, often mimicking other spongiotic disorders that can vesiculate. In addition to classically taught histopathologic clues, several unique characteristics were observed in our population. The presence of dermal neutrophils as the nonpredominant cell type (85%; n = 17 of 20) can serve as an additional clue to diagnosis. Deep inflammation (25%; n = 5 of 20) does not exclude a superficial diagnosis. The classically taught sandwich sign (32%; n = 8 of 25) may be less relevant in the setting of bullous tinea. Hyphae were most commonly seen within the stratum corneum adjacent to this blister rather than within the blister itself, and special staining was required in a substantial number of cases (40%; n = 10 of 25) to reach the correct diagnosis. Bullous tinea is unusual but should be considered in the differential diagnosis of blistering skin disorders. Hematoxylin and eosin-stained slides frequently lack obvious fungal hyphae; for this reason, periodic acid-Schiff reaction or Gomori/Grocott methenamine silver stains should be routinely considered for biopsies showing intraepidermal and/or subepidermal blister formation and prominent neutrophil infiltration to prevent misdiagnosis.

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