Review of Cutaneous Blastomycosis Seen in Wisconsin

Blastomycosis is a fungal infection caused by Blastomyces dermatitidis that is hyperendemic in Wisconsin. It commonly presents as a pulmonary infection and frequently disseminates to the skin. Studies evaluating the presentation and diagnosis of blastomycosis with skin as a presenting sign have not been thoroughly evaluated, and understanding the most accurate way to diagnose this infection is important for earlier therapeutic intervention.

This is a retrospective chart review study of a single institution. Subjects were identified through a search of ICD-9 (International Classification of Diseases, Ninth Revision) and ICD-10 (International Classification of Diseases, Tenth Revision) codes for blastomycosis in the clinical record and pathology database. Patients were included if diagnosed with cutaneous blastomycosis infection or involvement of the skin from systemic infection from January 1, 2009, to June 1, 2021.

Twenty patients with a diagnosis of cutaneous involvement of blastomycosis were identified; 65% (n = 13) were male. Median age of diagnosis was 55.5 years. Fifty-five percent of patients were White, 35% were Black or African American. In addition to residence in an endemic area, 50% (n = 10) had exposure risk factors. Fifty percent of patients (n = 10) initially presented with a skin concerns; 65% (n = 13) had extracutaneous involvement. Diagnosis was made by histopathology alone in 55% (n = 11), culture plus histopathology in 35% (n = 7), and culture alone in 5% (n = 1) of cases.

Our study highlighted similarities to those previously performed. Half of the patients (n = 10) who had cutaneous involvement of blastomycosis did not demonstrate clinically significant pulmonary involvement. Histopathology and culture remain critical in diagnosing cutaneous blastomycosis.