Is Hidradenitis Suppurativa an Autoimmune Disease?
The short answer is no - but the full answer is more nuanced and important for understanding why HS treatments work and how HS relates to other immune-mediated conditions.
Medical Disclaimer: This article is for educational purposes only and does not replace professional medical evaluation. Read full disclaimer.
Many people with hidradenitis suppurativa wonder whether their condition is an autoimmune disease - particularly because HS is treated with biologics that are also used for autoimmune conditions like rheumatoid arthritis and psoriasis. The answer requires understanding an important distinction in immunology between autoimmune and autoinflammatory diseases.
Autoimmune vs. Autoinflammatory: What Is the Difference?
| Feature | Autoimmune Disease | Autoinflammatory Disease |
|---|---|---|
| Primary driver | Adaptive immunity (T cells, B cells) | Innate immunity (neutrophils, macrophages) |
| Autoantibodies | Often present (e.g., ANA, RF) | Typically absent |
| Key cytokines | IL-2, IL-4, IFN-gamma | IL-1, IL-6, TNF-alpha, IL-17 |
| Examples | Lupus, RA, type 1 diabetes | HS, gout, familial Mediterranean fever |
| Biologic targets | B cells, T cells, IL-6 | TNF-alpha, IL-1, IL-17 |
HS is classified as an autoinflammatory disease because it involves dysregulation of innate immune responses - the body's first-line defense system - rather than adaptive immunity targeting self-tissue. Key inflammatory mediators in HS include TNF-alpha, IL-1-beta, IL-17, and IL-12/23, which are all targets of approved or investigational HS biologics.
What Goes Wrong in the HS Immune Response?
Follicular Occlusion Triggers Innate Immunity
The current understanding is that HS begins with occlusion (blockage) of hair follicles, leading to follicular rupture. This rupture releases follicular contents into the surrounding dermis, triggering a massive innate immune response involving neutrophils, macrophages, and mast cells.
IL-1 and the Inflammasome
Keratinocytes and macrophages in HS lesions show elevated NLRP3 inflammasome activation, leading to excessive IL-1-beta production. IL-1-beta is a master regulator of inflammation and drives many of the downstream inflammatory processes in HS.
IL-17 and Neutrophil Recruitment
IL-17A and IL-17F are markedly elevated in HS lesions and drive neutrophil recruitment, antimicrobial peptide production, and keratinocyte activation. Bimekizumab (Bimzelx) targets both IL-17A and IL-17F and is now FDA-approved for HS.
TNF-alpha and Systemic Inflammation
TNF-alpha is elevated both locally in HS lesions and systemically in the bloodstream of HS patients. TNF-alpha inhibitors (adalimumab/Humira) were the first FDA-approved biologic for HS and remain an important treatment option.
HS and Associated Immune-Mediated Conditions
While HS itself is autoinflammatory, it frequently co-occurs with both autoimmune and autoinflammatory conditions, suggesting shared immunological pathways. The metabolic comorbidities of HS, including diabetes and metabolic syndrome, also reflect this systemic inflammatory burden.
Crohn's Disease
AutoinflammatoryShares IL-12/23 and TNF-alpha pathways; anti-TNF biologics treat both
Spondyloarthropathy
Autoimmune/AutoinflammatoryJoint involvement in HS patients; IL-17 pathway shared
Pyoderma Gangrenosum
AutoinflammatoryPASH syndrome (PG + Acne + HS) is a recognized entity
Psoriasis
AutoinflammatoryShared IL-17 and TNF-alpha pathways; can coexist with HS
SAPHO Syndrome
AutoinflammatorySynovitis, acne, pustulosis, hyperostosis, osteitis - overlaps with HS
Thyroid Disease
AutoimmuneHigher prevalence in HS patients in some studies