Overview
Hidradenitis suppurativa (HS) is a chronic, relapsing inflammatory skin disease characterized by painful nodules, abscesses, and sinus tracts in apocrine gland-bearing skin (axillae, groin, inframammary folds). Long classified as a purely dermatological condition, emerging evidence reveals HS as a systemic inflammatory disorder with a significant gut microbiome component — connecting it to the broader gut-skin axis framework.
Microbiome Associations
Gut Microbiome
Mendelian randomization analysis has identified two gut taxa with causal risk effects on HS:
- Clostridium innocuum group — OR 2.17 (P = 0.00038); the strongest causal signal liu 2024 gut microbiota hidradenitis suppurativa mr
- lachnospira — OR 2.45 (P = 0.017); a paradoxical risk association for an SCFA-producing genus, suggesting that the mechanism may involve SCFA-mediated alteration of cutaneous immune responses rather than simple inflammation liu 2024 gut microbiota hidradenitis suppurativa mr
Remarkably, 40% of HS patients harbor a gut microbiota configuration similar to Crohn's disease, characterized by enrichment of pathogenic genera and depletion of beneficial genera including faecalibacterium prausnitzii cronin 2023 diet microbiome crohns hidradenitis. This overlap is consistent with clinical observations that HS and CD frequently co-occur and share TNF-alpha-driven pathology.
Skin Microbiome
The HS lesional skin microbiome shows enrichment of anaerobic and biofilm-forming organisms in sinus tracts, including Prevotella, Porphyromonas, and coagulase-negative staphylococci. The tunneling nature of HS sinus tracts creates anaerobic microenvironments that may select for specific pathobiont communities — paralleling the oxygen-dependent ecological dynamics seen in gut dysbiosis.
Metal Associations
Direct metal studies in HS are limited. However, the strong overlap with Crohn's disease microbiome patterns and shared TNF-alpha-driven inflammation suggest that metal-microbiome dynamics relevant to CD — including iron-siderophore competition and zinc-dependent metalloprotease activity — may operate in HS as well. Nickel allergy, which is highly prevalent in inflammatory skin conditions, has not been systematically studied in HS but represents a plausible connection given nickel's role in immune sensitization.
Associated Conditions
- crohns disease — 40% gut microbiota overlap; shared TNF-alpha pathology; clinical co-occurrence well-documented. Both conditions respond to anti-TNF therapy (adalimumab is approved for both).
Environmental Factors
- Diet — Western diet patterns (high-fat, low-fiber) are associated with HS severity, consistent with the gut-microbiome-mediated mechanism
- Smoking — Strong independent risk factor; may influence both skin and gut microbiome composition
- Obesity — Mechanical and inflammatory contributor; shared metabolic endotoxemia pathway
Key Studies
- liu 2024 gut microbiota hidradenitis suppurativa mr — Two-sample MR identifying causal gut taxa (cross-sectional/MR design)
- cronin 2023 diet microbiome crohns hidradenitis — 40% HS-CD gut microbiome overlap
Open Questions
- Does the Lachnospira risk association operate through SCFA-mediated cutaneous immune modulation, or through a different mechanism?
- Would dietary interventions targeting the gut microbiome (fiber supplementation, Mediterranean diet) improve HS outcomes?
- Are the shared CD-HS microbiome features a cause or consequence of shared genetic susceptibility at TNF pathway loci?
Cross-References
- crohns disease — shared gut microbiome configuration and TNF-alpha pathology
- lachnospira — causal risk factor via MR analysis
- faecalibacterium prausnitzii — depleted in HS gut microbiome (CD-like pattern)
- barrier-dysfunction — gut permeability as route for systemic inflammation affecting skin