Scedosporium/Pseudallescheria Infections

The genus Scedosporium comprises a group of filamentous fungi found ubiquitously in the environment. The two major human pathogens within this genus are S. apiospermum-the asexual state of Pseudallescheria boydii - and S. prolificans. Both histologically resemble Aspergillus species, with hyphae that are septated and branching at acute angles. Although Scedosporium infections can occur in immunocompetent persons, the overall incidence has increased over the last decade as a consequence of improved diagnostics and a growing immunosuppressed population (e.g., transplant, malignancy, acquired immunodeficiency syndrome). These organisms can cause systemic infection in immunocompromised hosts manifested as sinopulmonary, central nervous system, osteoarticular, ocular, endovascular, and lymphocutaneous disease. Dissemination may occur hematogenously or contiguously, with high associated mortality (>75%). Scedosporium species are known to be largely resistant to traditional antifungals such as amphotericin B; however, treatment with newer triazoles, such as voriconazole, appears to be more efficacious.