Bilateral Auricular Blastomycosis-like Pyoderma: A Rare Presentation Histologically Misinterpreted as Squamous Cell Carcinoma.

Abstract

Blastomycosis-like pyoderma (BLP) is a rare chronic inflammatory dermatosis characterized by exuberant vegetative and verrucous plaques, most frequently associated with bacterial colonization, particularly Staphylococcus aureus. Owing to its striking clinical and histopathological resemblance to squamous cell carcinoma (SCC) and other granulomatous or hyperplastic dermatoses, BLP represents a well-recognized diagnostic pitfall, often leading to delayed diagnosis or unnecessary surgical management. We report an unusual case of bilateral auricular BLP in a 58-year-old apparently immunocompetent woman, initially misdiagnosed as SCC. Comprehensive clinicopathological reassessment revealed pseudoepitheliomatous hyperplasia, intraepidermal neutrophilic microabscesses, and a dense mixed inflammatory infiltrate, findings consistent with a reactive rather than neoplastic process. Microbiological cultures confirmed Staphylococcus aureus, supporting the final diagnosis of BLP and guiding effective antimicrobial therapy. To better contextualize this rare presentation, we reviewed all previously reported cases of BLP, summarizing available clinical, histopathological, microbiological, and therapeutic data. This case further raises the possibility of an association between BLP and systemic inflammatory conditions, as the patient subsequently developed severe colitis, highlighting the potential role of immune dysregulation and the gut-skin axis in disease pathogenesis or a possible temporal association, without allowing causal inference. Beyond inflammatory bowel disease, blastomycosis-like pyoderma has been reported in association with a variety of systemic and immune-mediated conditions, including diabetes mellitus, hematologic malignancies, HIV infection, chronic renal failure, autoimmune disorders, and prolonged immunosuppressive therapies. These associations support the concept that BLP represents a hyperinflammatory reaction pattern occurring in the setting of altered immune surveillance rather than a purely infectious disease. Accurate recognition and management of BLP require careful integration of clinical features, histological findings, and microbiological results. Increased awareness of its diverse presentations is essential to avoid misdiagnosis and to ensure appropriate, conservative treatment.