Sporotrichosis: Case report and review of sporotrichosis — clinical presentation, diagnosis, antifungal susceptibility, and United States epidemiology

Sporotrichosis is a subacute to chronic fungal infection caused by Sporothrix species, typically presenting with cutaneous or lymphocutaneous disease. Although traditionally associated with Latin America, zoonotic and environmental transmission has become increasingly recognized in the United States, with rising reports linked to S. schenckii and S. brasiliensis. Clinical awareness remains limited, and diagnostic delays are common.

Case Presentation: We describe a case of cutaneous sporotrichosis in a previously healthy adult in the southeastern United States who presented with progressive nodular lesions along lymphatic channels following presumed traumatic inoculation. Initial bacterial cultures were negative, and the patient failed empiric antibacterial therapy. Fungal culture ultimately yielded Sporothrix species. Histopathology demonstrated suppurative granulomatous inflammation with cigar-shaped yeasts. Antifungal susceptibility testing revealed elevated MICs to itraconazole and fluconazole but low MICs to posaconazole and amphotericin B. The patient responded to prolonged itraconazole therapy with clinical resolution.

Discussion: This case highlights key diagnostic challenges including delayed suspicion, variable antigen detection performance, and the need for culture-based confirmation. We review U.S. epidemiologic trends demonstrating geographic expansion of sporotrichosis, potential emergence of S. brasiliensis, and increased zoonotic clusters involving companion animals. Antifungal susceptibility patterns vary widely by species; itraconazole remains first-line therapy, though rising MICs may necessitate alternative azoles. Early recognition is essential to shorten time to diagnosis, guide antifungal selection, and prevent disease progression.

Conclusion: Sporotrichosis remains an under-recognized infection in the United States. This case underscores the importance of considering fungal etiologies in chronic nodular skin lesions and the role of species-level identification and susceptibility testing. Enhanced epidemiologic surveillance is needed as the geographic distribution and antifungal resistance patterns continue to evolve.