Unveiling the Microbiome's Role in Hidradenitis Suppurativa: A Comprehensive Review of Pathogenetic Mechanisms

Hidradenitis suppurativa (HS) is a chronic, recurrent, and highly debilitating inflammatory disorder of the pilosebaceous unit. Its pathogenesis is considered multifactorial, involving genetic, environmental, hormonal, lifestyle, and microbiome-related factors. The microbiota, defined as the collection of microorganisms, their genomes, and their interactions within a given environment, colonizes multiple sites of the healthy human body, which include the skin and gut, where it contributes to the maintenance of homeostasis. In HS, both skin and gut microbiota exhibit disruptions in composition and diversity, a state referred to as dysbiosis. Alterations in the expression of antimicrobial peptides in HS further implicate the microbiome in disease pathophysiology. In addition, chronic inflammation, bacterial biofilm formation, and dysbiosis are thought to contribute to the severity and recurrence of HS. Although the precise role of dysbiosis in HS pathogenesis remains unclear, several studies have demonstrated a reduction in cutaneous microbial diversity in HS patients, distinguished by an increased abundance of anaerobic and opportunistic bacteria and a reduction in commensal species. The intestinal microbiome has been even less thoroughly investigated, but available evidence suggests decreased overall diversity and richness, with enrichment of pro-inflammatory and depletion of anti-inflammatory bacterial taxa. This review aims to provide an overview of the current knowledge regarding the role of the microbiome in HS, with the goal of informing the direction of future research, including the potential utility of the microbiome as a biomarker for diagnosis and severity stratification in HS.