Thinking Beyond Bacterial Infection: A Case of Cutaneous Blastomycosis

Blastomycosis is caused by Blastomyces dermatitidis, a dimorphic fungus that primarily causes pulmonary disease. Cutaneous blastomycosis is infrequent and tends to be misdiagnosed given its similar presentation to other cutaneous fungal infections and malignancies. A 51-year-old woman presented with a two-month history of disfiguring nasal lesions. The patient had a past medical history of cervical cancer which was currently in remission. Social history was significant for frequent travel throughout the United States as a truck driver, including the Midwest. The patient had a non-purulent verrucous plaque on her right nare, which was painless and mildly pruritic. Superficial cultures grew Enterococcus faecalis, prompting treatment with oral cephalexin and topical mupirocin. Given no relief, the patient was started on clindamycin followed by Augmentin. Both treatments were unsuccessful.  The lesion was then biopsied and fungal cultures were sent. The biopsy showed broad-based budding yeast surrounded by pseudoepitheliomatous hyperplasia, and cultures grew Blastomyces dermatitidis. The patient was initiated on 200 mg itraconazole thrice daily for the first three days, followed by 200 mg itraconazole twice daily for the next 12 months. She showed notable improvement within a month. This patient was initially misdiagnosed with bacterial infection due to superficial cultures, which were likely a contaminant. It was only after a biopsy that the patient was accurately diagnosed. Besides bacterial infection, cutaneous blastomycosis is often confused with coccidioidomycosis, mycobacterial infection, or squamous cell carcinoma. In patients such as ours who are presenting with persistent facial lesions in the setting of frequent travel history, fungal etiologies should be high on the differential. A biopsy and fungal cultures should be sent at the outset for accurate diagnosis and treatment.