Facial Skin Mycobiome in Atopic Dermatitis With and Without Facial Involvement and Healthy Controls: A Case–Control Study

With the growing interest in the skin microbiome in atopic dermatitis (AD), alterations in cutaneous fungal communities have garnered increasing attention. However, their role in AD pathogenesis and their association with clinical parameters remain unclear. This study characterised the facial skin mycobiome in AD patients with and without facial involvement, compared to healthy controls. Fungal composition was analysed across multiple taxonomic levels, along with assessments of alpha and beta diversity and predicted functional pathways. Basidiomycota and Ascomycota were the predominant phyla across all groups, with Malassezia as the dominant genus. At the species level, Malassezia_globosa and Malassezia_japonica were enriched in AD patients with facial involvement, whereas Malassezia_restricta was reduced compared with the other groups. In the full cohort, no significant differences in overall fungal diversity were observed; however, richness-based alpha diversity indices differed between facial AD and healthy controls in an adult-only sensitivity analysis, while Shannon and Simpson indices remained comparable. Notably, distinct differences in predicted metabolic pathways were identified among groups. Correlation analyses showed that Malassezia_restricta abundance was positively associated with body mass index (BMI), whereas Malassezia_globosa was negatively associated with disease severity. Collectively, these findings indicate that facial AD is associated with distinct mycobiome alterations, with potential age-related effects on specific taxa and diversity metrics. Further longitudinal and mechanistic studies are warranted to elucidate causal relationships and explore therapeutic implications.