Blastomycosis-like pyoderma.

Seven patients with blastomycosis-like pyoderma had skin lesions of four months' to six years' duration. The criteria for the diagnosis of blastomycosis-like pyoderma include the clinical presentation of large verrucous plaques with multiple pustules and elevated border, pseudoepitheliomatous hyperplasia with abscess histologically, and the growth of at least one pathogenic bacteria from the culture of a tissue-biopsy specimen. The differential diagnosis includes deep fungus infection (especially North American blastomycosis), bromoderma, pyoderma gangrenosum, mycobacterial infections, giant keratoacanthoma, and squamous cell carcinoma. Generally, the patients had one or more conditions that could have affected their systemic or local immunologic competence to infection. We believe that the clinical and histologic features in these cases of blastomycosis-like pyoderma were produced by an unusual, exaggerated, vegetating-tissue reaction to a primary or secondary bacterial infection.