International Session 54　　Miscellaneous 2

Fungal ball is a unilateral form of chronic rhinosinusitis with a confined microenvironment.Whether fungal communities differ between lesional and contralateral sinuses remains unclear.This study compared paired fungal microbiota and functional signatures using ITS sequencing.Patients with pathologically confirmed fungal ball undergoing endoscopic sinus surgery were prospectively enrolled.Paired middle-meatus samples were analyzed for diversity indices, taxonomic profiles, and PICRUSt2-inferred pathways.Beta diversity differed significantly between lesional and contralateral sites(p＝0． 041) , while alpha diversity showed no difference.Although Aspergillus is the principal fungal ball component, its abundance did not differ between sides.Functional analysis revealed enrichment of the monoterpenoid biosynthesis pathway in lesional samples(p＝0． 037) .Paired ITS profiling demonstrated localized shifts in fungal composition and predicted functions.These changes may reflect microenvironmental alterations secondary to Aspergillus-related obstruction rather than overgrowth.Further studies are needed to clarify these mechanisms.