First Report of Fatal Disseminated Blastomyces percursus Infection in a Liver Transplant Recipient in Iran, a Non-endemic Country: A Case Report.

Blastomycosis is an invasive dimorphic fungal infection capable of causing severe disseminated disease in immunocompromised hosts. Although traditionally endemic to North America, increasing molecular evidence suggests a broader geographic distribution. Iran is not considered endemic, and no prior species-level confirmed cases of Blastomyces percursus have been reported. We report a 31-year-old liver transplant recipient who developed progressive diffuse papulopustular and verrucous necrotic cutaneous lesions 17 months after transplantation. Initial diagnostic evaluation was inconclusive. Detection of fungal DNA consistent with Aspergillus species in skin biopsy specimens prompted initiation of voriconazole therapy; however, the clinical course progressed despite treatment. The patient subsequently developed severe weight loss, high-level cytomegalovirus (CMV) viremia, pulmonary nodules, and mucosal involvement. Initial fungal culture suggested Pseudallescheria boydii, but re-evaluation at a reference mycology laboratory raised suspicion for blastomycosis. Definitive species identification was achieved by amplification and Sanger sequencing of the internal transcribed spacer (ITS1-5.8S-ITS2) region. The 520-bp sequence demonstrated 99.6-100% identity with reference Blastomyces percursus strains, and phylogenetic analysis confirmed clustering within the B. percursus clade. Despite targeted antifungal therapy with liposomal amphotericin B and antiviral treatment for CMV disease, the infection progressed to disseminated involvement with central nervous system manifestations, resulting in a fatal outcome. This case highlights the diagnostic complexity of invasive fungal infections in non-endemic regions and emphasizes the importance of early molecular identification in immunocompromised patients presenting with atypical cutaneous and systemic fungal disease.