A Possible Role of Mycobiome in the Pathophysiology of Acne: Structured Narrative Review and Perspectives

Acne vulgaris pathogenesis involves complex interactions between sebum hypersecretion, follicular hyperkeratinisation, microbial colonisation and inflammatory cascades. While the bacterial microbiome has been extensively studied, the role of the skin mycobiome, particularly lipophilic Malassezia species, remains less clearly defined in acne-prone sites. To evaluate evidence for skin mycobiome involvement in acne pathogenesis, a structured narrative review was conducted in PubMed/MEDLINE and PMC, synthesising findings from 14 cross-sectional studies involving 1650 participants from diverse geographic and ancestry backgrounds. Across sequencing and culture-based studies, Malassezia was the dominant fungal genus on healthy as well as acne-prone skin; species-level data most often identified M. restricta and M. globosa, with occasional reports of M. furfur. Although significant variations were observed in fungal abundance, discrepancies exist between studies due to differences in study design, sampling methods (surface swabs vs. comedone or pustule contents vs. pore strips), culture media (lipid-supplemented vs. standard), molecular target (ITS1 rDNA vs. other loci) and population demographics. Multiple sequencing studies did not detect significant fungal alpha/beta-diversity differences between acne and non-acne skin while confirming Malassezia species dominance. One study highlighted the potential underdiagnosis of Malassezia folliculitis in acne patients, suggesting that misdiagnosis may occur due to overlapping clinical presentations. Future studies should predefine primary outcomes, adjust for multiplicity, report sampling depth (surface vs. follicular), specify fungal rDNA region sequenced, use specific lipid-supplemented media for Malassezia isolation when culturing, co-profile bacteria and fungi, and add systematic clinical assessment of Malassezia folliculitis.