name: Hidradenitis Suppurativa
creation_date: "2026-03-09T20:00:00Z"
updated_date: "2026-03-10T02:00:00Z"
category: Complex
parents:
- Dermatological Disease
- Inflammatory Disease
disease_term:
  preferred_term: hidradenitis suppurativa
  term:
    id: MONDO:0006559
    label: hidradenitis suppurativa
synonyms:
- Acne Inversa
- Verneuil Disease
- Apocrine Acne
stages:
- name: Hurley Stage I
  description: Solitary or multiple isolated abscess formation without sinus tracts or scarring. The earliest phase where structural skin changes have not yet occurred, though disease progression varies among patients.
  evidence:
  - reference: PMID:41678402
    reference_title: "Assessing disease progression in Hurley I hidradenitis suppurativa patients: a nested case-control study."
    supports: SUPPORT
    snippet: "In Hurley stage I, the earliest phase, structural changes have not yet occurred. However, disease progression varies among patients; some remain indefinitely at this stage, while others advance to more severe forms."
    explanation: "Characterizes Hurley Stage I as the earliest phase without structural changes, with variable progression risk."
    evidence_source: HUMAN_CLINICAL
- name: Hurley Stage II
  description: Recurrent abscesses with sinus tract formation and scarring, separated by normal skin. Most patients present at this stage at diagnosis.
  evidence:
  - reference: PMID:41677500
    reference_title: "Clinical Characteristics and Management of Pediatric Hidradenitis Suppurativa: A Canadian Single-Centre Multidisciplinary Experience."
    supports: SUPPORT
    snippet: "Most had Hurley stage II (60.5%) or III (28.9%) disease."
    explanation: "Clinical data showing Hurley Stage II as the most common presentation at diagnosis."
    evidence_source: HUMAN_CLINICAL
  - reference: PMID:41229081
    reference_title: "Surgical Interventions in Advanced Hidradenitis Suppurativa: A Systematic Review."
    supports: SUPPORT
    snippet: "In patients with moderate-to-severe disease (Hurley Stages II and III), surgical intervention is frequently required to achieve durable disease control."
    explanation: "Confirms Hurley Stage II represents moderate disease often requiring surgical management."
    evidence_source: HUMAN_CLINICAL
- name: Hurley Stage III
  description: Diffuse or broad involvement with multiple interconnected sinus tracts and abscesses across an entire region. Represents the most severe form requiring aggressive surgical intervention.
  evidence:
  - reference: PMID:41229081
    reference_title: "Surgical Interventions in Advanced Hidradenitis Suppurativa: A Systematic Review."
    supports: SUPPORT
    snippet: "In patients with moderate-to-severe disease (Hurley Stages II and III), surgical intervention is frequently required to achieve durable disease control."
    explanation: "Confirms Hurley Stage III as severe disease requiring surgical intervention for disease control."
    evidence_source: HUMAN_CLINICAL
  - reference: PMID:41677500
    reference_title: "Clinical Characteristics and Management of Pediatric Hidradenitis Suppurativa: A Canadian Single-Centre Multidisciplinary Experience."
    supports: SUPPORT
    snippet: "Most had Hurley stage II (60.5%) or III (28.9%) disease."
    explanation: "Clinical data showing Hurley Stage III represents approximately 29% of patients at diagnosis in a referral cohort."
    evidence_source: HUMAN_CLINICAL
pathophysiology:
- name: Follicular Hyperkeratosis
  description: >
    Aberrant keratinization of the hair follicle infundibulum leads to follicular
    plugging. Hyperproliferative keratinocytes produce excess keratin that occludes
    the follicular ostium. This is the initiating event in HS pathogenesis.
  role: Primary
  cell_types:
  - preferred_term: Keratinocyte
    term:
      id: CL:0000312
      label: keratinocyte
  biological_processes:
  - preferred_term: Keratinization
    modifier: ABNORMAL
    term:
      id: GO:0031424
      label: keratinization
  downstream:
  - target: Follicular Rupture
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:34409324
      reference_title: "Hidradenitis suppurativa is an autoinflammatory keratinization disease: A review of the clinical, histologic, and molecular evidence."
      supports: SUPPORT
      snippet: "Follicular hyperkeratosis/occlusion and perifollicular inflammation coexist in histologic specimens, with interleukin 1α demonstrated to stimulate comedogenesis in the infundibulum."
      explanation: "Follicular hyperkeratosis/occlusion leads to follicular dilation and rupture, with IL-1α-driven comedogenesis in the infundibulum."
      evidence_source: HUMAN_CLINICAL
  evidence:
  - reference: PMID:34409324
    reference_title: "Hidradenitis suppurativa is an autoinflammatory keratinization disease: A review of the clinical, histologic, and molecular evidence."
    supports: SUPPORT
    snippet: "The pathogenic model of hidradenitis suppurativa is in the midst of a paradigm shift away from a disorder of primary follicular occlusion to an autoinflammatory keratinization disease."
    explanation: "Comprehensive review establishing follicular keratinization as a key pathogenic event in HS, whether as primary occlusion or secondary to inflammation."
    evidence_source: HUMAN_CLINICAL
  - reference: PMID:20929727
    reference_title: "Gamma-secretase gene mutations in familial acne inversa."
    supports: SUPPORT
    snippet: "Acne inversa (AI), also known as hidradenitis suppurativa, is a chronic, recurrent, inflammatory disease of hair follicles that often runs in families."
    explanation: "This landmark paper identifies HS as a disease of hair follicles, consistent with follicular occlusion as the primary pathological event."
    evidence_source: HUMAN_CLINICAL
- name: Follicular Rupture
  description: >
    Continued keratinization causes follicular dilation and eventual mechanical
    rupture, releasing keratin, commensal bacteria, and damage-associated
    molecular patterns (DAMPs) into the surrounding dermis. This triggers
    the innate immune response.
  downstream:
  - target: Innate Immune Hyperactivation
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:39274425
      reference_title: "Evidence on Hidradenitis Suppurativa as an Autoinflammatory Skin Disease."
      supports: SUPPORT
      snippet: "In the early phase of the disease, the innate immune system is hyperactivated, contributing to tissue damage and triggering the activation and amplification of the adaptive immune response, which plays a pivotal role in the chronic stages of the disease."
      explanation: "Follicular rupture directly triggers innate immune hyperactivation as the early disease phase."
      evidence_source: HUMAN_CLINICAL
  - target: Epigenetic Reprogramming of Keratinocytes
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:38011564
      reference_title: "Epigenetic switch reshapes epithelial progenitor cell signatures and drives inflammatory pathogenesis in hidradenitis suppurativa."
      supports: SUPPORT
      snippet: "we investigated HS epithelial cells and demonstrated that HS basal progenitors modulate their lineage restriction and give rise to pathogenic keratinocyte clones, resulting in epidermal hyperproliferation and dysregulated inflammation in HS."
      explanation: "Epigenetic reprogramming of keratinocytes occurs in the context of HS lesional skin, likely triggered by follicular disruption."
      evidence_source: HUMAN_CLINICAL
  evidence:
  - reference: PMID:34409324
    reference_title: "Hidradenitis suppurativa is an autoinflammatory keratinization disease: A review of the clinical, histologic, and molecular evidence."
    supports: SUPPORT
    snippet: "The process of follicular rupture and dermal tunnel formation can be explained as secondary responses to inflammatory activation of fibroblasts and epithelial-mesenchymal transition, with antibody production associated with inflammatory amplification in advanced disease."
    explanation: "Establishes follicular rupture as a key pathogenic event in HS, releasing keratin and DAMPs into the dermis."
    evidence_source: HUMAN_CLINICAL
- name: Innate Immune Hyperactivation
  description: >
    Following follicular rupture, DAMPs and PAMPs activate TLR2 and inflammasome
    pathways (NLRP3/CASP1). This drives IL-1beta and IL-36 release from
    keratinocytes and myeloid cells, recruiting neutrophils and macrophages
    to form the early inflammatory infiltrate and abscess.
  cell_types:
  - preferred_term: Neutrophil
    term:
      id: CL:0000775
      label: neutrophil
  - preferred_term: Macrophage
    term:
      id: CL:0000235
      label: macrophage
  biological_processes:
  - preferred_term: Innate Immune Response
    modifier: INCREASED
    term:
      id: GO:0045087
      label: innate immune response
  - preferred_term: Inflammatory Response
    modifier: INCREASED
    term:
      id: GO:0006954
      label: inflammatory response
  downstream:
  - target: Th17-Driven Adaptive Inflammation
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - IL-23 production by dendritic cells drives Th17 polarization
    evidence:
    - reference: PMID:39274425
      reference_title: "Evidence on Hidradenitis Suppurativa as an Autoinflammatory Skin Disease."
      supports: SUPPORT
      snippet: "In the early phase of the disease, the innate immune system is hyperactivated, contributing to tissue damage and triggering the activation and amplification of the adaptive immune response, which plays a pivotal role in the chronic stages of the disease."
      explanation: "Innate immune activation triggers and amplifies the adaptive (Th17) immune response."
      evidence_source: HUMAN_CLINICAL
  - target: Abscess Formation
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:34409324
      reference_title: "Hidradenitis suppurativa is an autoinflammatory keratinization disease: A review of the clinical, histologic, and molecular evidence."
      supports: SUPPORT
      snippet: "Known metabolic comorbidities and smoking are known to upregulate interleukin 1α in follicular keratinocytes."
      explanation: "IL-1α upregulation drives neutrophil recruitment and abscess formation through innate immune activation."
      evidence_source: HUMAN_CLINICAL
  evidence:
  - reference: PMID:39274425
    reference_title: "Evidence on Hidradenitis Suppurativa as an Autoinflammatory Skin Disease."
    supports: SUPPORT
    snippet: "In the early phase of the disease, the innate immune system is hyperactivated, contributing to tissue damage and triggering the activation and amplification of the adaptive immune response, which plays a pivotal role in the chronic stages of the disease."
    explanation: "Directly supports the sequential innate-then-adaptive immune dysregulation model in HS pathogenesis."
    evidence_source: HUMAN_CLINICAL
  - reference: PMID:37957373
    reference_title: "IRAK4 degrader in hidradenitis suppurativa and atopic dermatitis: a phase 1 trial."
    supports: SUPPORT
    snippet: "Toll-like receptor-driven and interleukin-1 (IL-1) receptor-driven inflammation mediated by IL-1 receptor-associated kinase 4 (IRAK4) is involved in the pathophysiology of hidradenitis suppurativa (HS) and atopic dermatitis (AD)."
    explanation: "Demonstrates TLR/IL-1R-driven innate immune activation as central to HS pathophysiology."
    evidence_source: HUMAN_CLINICAL
- name: Abscess Formation
  description: >
    Neutrophilic infiltration at the site of follicular rupture leads to
    abscess formation. Dense collections of neutrophils, cellular debris, and
    purulent material form painful nodules in intertriginous skin.
  cell_types:
  - preferred_term: Neutrophil
    term:
      id: CL:0000775
      label: neutrophil
  downstream:
  - target: Tissue Destruction and Scarring
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:23439959
      reference_title: "Acne inversa (Hidradenitis suppurativa): A review with a focus on pathogenesis and treatment."
      supports: SUPPORT
      snippet: "Acne inversa (AI) is a disabilitating chronic inflammatory disease with major negative impact on quality of life and significant co-morbidities."
      explanation: "Recurrent abscess formation causes cumulative tissue destruction and scarring."
      evidence_source: HUMAN_CLINICAL
  - target: Sinus Tract Formation
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Recurrent abscess cycles with chronic inflammation
    evidence:
    - reference: PMID:41678402
      reference_title: "Assessing disease progression in Hurley I hidradenitis suppurativa patients: a nested case-control study."
      supports: SUPPORT
      snippet: "the increase in abscess count from baseline (categorical) (p = 0.0003)."
      explanation: "Increasing abscess count is a predictor of disease progression to sinus tract formation."
      evidence_source: HUMAN_CLINICAL
  - target: Recurrent Skin Abscesses
    causal_link_type: DIRECT
    description: Neutrophilic abscess formation directly manifests as the recurrent skin abscess phenotype.
    evidence:
    - reference: PMID:29183082
      reference_title: "Hidradenitis Suppurativa: Advances in Diagnosis and Treatment."
      supports: SUPPORT
      snippet: "The diagnosis of HS is made by lesion morphology (nodules, abscesses, tunnels, and scars), location (axillae, inframammary folds, groin, perigenital, or perineal), and lesion progression (2 recurrences within 6 months or chronic or persistent lesions for ≥3 months)."
      explanation: "Recurrent abscesses are a defining diagnostic criterion for HS, directly linking the pathophysiology of abscess formation to the clinical phenotype."
      evidence_source: HUMAN_CLINICAL
  - target: Chronic Pain
    causal_link_type: DIRECT
    description: Painful abscesses are a major contributor to chronic pain in HS patients.
    evidence:
    - reference: PMID:23439959
      reference_title: "Acne inversa (Hidradenitis suppurativa): A review with a focus on pathogenesis and treatment."
      supports: SUPPORT
      snippet: "Acne inversa (AI) is a disabilitating chronic inflammatory disease with major negative impact on quality of life and significant co-morbidities."
      explanation: "Debilitating nature and quality of life impact directly supports abscesses causing chronic pain."
      evidence_source: HUMAN_CLINICAL
  evidence:
  - reference: PMID:29183082
    reference_title: "Hidradenitis Suppurativa: Advances in Diagnosis and Treatment."
    supports: SUPPORT
    snippet: "The diagnosis of HS is made by lesion morphology (nodules, abscesses, tunnels, and scars), location (axillae, inframammary folds, groin, perigenital, or perineal), and lesion progression (2 recurrences within 6 months or chronic or persistent lesions for ≥3 months)."
    explanation: "Abscess formation is a cardinal diagnostic feature of HS, part of the defining lesion morphology."
    evidence_source: HUMAN_CLINICAL
- name: Th17-Driven Adaptive Inflammation
  description: >
    IL-23 from dendritic cells drives Th17 polarization. IL-17A/F-producing
    T cells amplify neutrophil recruitment via CXCL1/8 and sustain chronic
    inflammation. The Th17:Treg imbalance perpetuates the inflammatory cycle.
  cell_types:
  - preferred_term: T-helper 17 Cell
    term:
      id: CL:0000899
      label: T-helper 17 cell
  biological_processes:
  - preferred_term: T-helper 17 Cell Differentiation
    modifier: INCREASED
    term:
      id: GO:0072539
      label: T-helper 17 cell differentiation
  downstream:
  - target: Tertiary Lymphoid Structure Formation
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Sustained cytokine milieu activates fibroblast chemokine programs
    evidence:
    - reference: PMID:39662091
      reference_title: "Skin immune-mesenchymal interplay within tertiary lymphoid structures promotes autoimmune pathogenesis in hidradenitis suppurativa."
      supports: SUPPORT
      snippet: "These TLSs were enriched with proliferative T cells, including follicular helper (Tfh), regulatory (Treg), and pathogenic T cells (IL17A+ and IFNG+), alongside extensive clonal expansion of plasma cells producing antibodies reactive to keratinocytes."
      explanation: "IL-17A+ pathogenic T cells within TLSs demonstrate the link between Th17 inflammation and TLS formation."
      evidence_source: HUMAN_CLINICAL
  evidence:
  - reference: DOI:10.3390/biomedicines12020338
    supports: SUPPORT
    snippet: "The dysregulation of immune mediators, including TNF-α, IL-17, IL-1β, and IL-12/23, plays a crucial role in the chronic inflammatory nature of HS."
    explanation: "Confirms the key cytokines involved in HS immune dysregulation including the IL-17 axis."
    evidence_source: HUMAN_CLINICAL
  - reference: PMID:39662091
    reference_title: "Skin immune-mesenchymal interplay within tertiary lymphoid structures promotes autoimmune pathogenesis in hidradenitis suppurativa."
    supports: SUPPORT
    snippet: "These TLSs were enriched with proliferative T cells, including follicular helper (Tfh), regulatory (Treg), and pathogenic T cells (IL17A+ and IFNG+), alongside extensive clonal expansion of plasma cells producing antibodies reactive to keratinocytes."
    explanation: "Confirms IL-17A+ pathogenic T cells as key components of the HS inflammatory infiltrate."
    evidence_source: HUMAN_CLINICAL
- name: Epigenetic Reprogramming of Keratinocytes
  description: >
    HS basal progenitor keratinocytes undergo epigenetic rewiring with extensive
    chromatin remodeling (1,434 gained / 3,722 lost ATAC peaks) that primes
    inflammatory gene programs. This produces pathogenic keratinocyte clones
    marked by S100A7/8/9 and KRT6 that trigger IL-1, IL-10, and complement
    cascades. This represents an epithelial-intrinsic disease driver.
  cell_types:
  - preferred_term: Keratinocyte
    term:
      id: CL:0000312
      label: keratinocyte
  biological_processes:
  - preferred_term: Cell Population Proliferation
    modifier: INCREASED
    term:
      id: GO:0008283
      label: cell population proliferation
  downstream:
  - target: Innate Immune Hyperactivation
    causal_link_type: DIRECT
    description: Pathogenic keratinocytes produce IL-1 and complement that amplify innate immune activation.
    evidence:
    - reference: PMID:38011564
      reference_title: "Epigenetic switch reshapes epithelial progenitor cell signatures and drives inflammatory pathogenesis in hidradenitis suppurativa."
      supports: SUPPORT
      snippet: "we identified a keratinocyte population specific to HS. This population is marked by S100A7/8/9 and KRT6 family members, triggering IL1, IL10, and complement inflammatory cascades."
      explanation: "Pathogenic keratinocytes directly trigger IL-1 and complement cascades that drive innate immune hyperactivation."
      evidence_source: HUMAN_CLINICAL
  evidence:
  - reference: PMID:38011564
    reference_title: "Epigenetic switch reshapes epithelial progenitor cell signatures and drives inflammatory pathogenesis in hidradenitis suppurativa."
    supports: SUPPORT
    snippet: "we investigated HS epithelial cells and demonstrated that HS basal progenitors modulate their lineage restriction and give rise to pathogenic keratinocyte clones, resulting in epidermal hyperproliferation and dysregulated inflammation in HS."
    explanation: "Directly demonstrates epigenetic reprogramming of basal progenitors giving rise to pathogenic keratinocyte clones in HS."
    evidence_source: HUMAN_CLINICAL
  - reference: PMID:38011564
    reference_title: "Epigenetic switch reshapes epithelial progenitor cell signatures and drives inflammatory pathogenesis in hidradenitis suppurativa."
    supports: SUPPORT
    snippet: "we identified a keratinocyte population specific to HS. This population is marked by S100A7/8/9 and KRT6 family members, triggering IL1, IL10, and complement inflammatory cascades."
    explanation: "Identifies the specific pathogenic keratinocyte population and the inflammatory cascades it drives."
    evidence_source: HUMAN_CLINICAL
- name: Tertiary Lymphoid Structure Formation
  description: >
    In chronic HS lesions, organized tertiary lymphoid structures (TLSs) form near
    epithelialized tunnels. These TLSs contain proliferative T cells (including Tfh,
    Treg, and IL-17A+/IFNG+ pathogenic T cells) and clonally expanded plasma cells
    producing anti-keratinocyte autoantibodies. HS fibroblasts expressing CXCL13 or
    CCL19 orchestrate lymphocyte aggregation via TNF-alpha feedback loops.
  cell_types:
  - preferred_term: Plasma Cell
    term:
      id: CL:0000786
      label: plasma cell
  - preferred_term: Fibroblast
    term:
      id: CL:0000057
      label: fibroblast
  biological_processes:
  - preferred_term: Adaptive Immune Response
    modifier: DYSREGULATED
    term:
      id: GO:0002250
      label: adaptive immune response
  downstream:
  - target: Tissue Destruction and Scarring
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Autoantibodies and complement activation damage tissue
    - NET formation contributes to tissue destruction
    evidence:
    - reference: PMID:39662091
      reference_title: "Skin immune-mesenchymal interplay within tertiary lymphoid structures promotes autoimmune pathogenesis in hidradenitis suppurativa."
      supports: SUPPORT
      snippet: "extensive clonal expansion of plasma cells producing antibodies reactive to keratinocytes."
      explanation: "Anti-keratinocyte autoantibodies from TLS-derived plasma cells contribute to tissue destruction."
      evidence_source: HUMAN_CLINICAL
  evidence:
  - reference: PMID:39662091
    reference_title: "Skin immune-mesenchymal interplay within tertiary lymphoid structures promotes autoimmune pathogenesis in hidradenitis suppurativa."
    supports: SUPPORT
    snippet: "Multi-omics profiling and multiplexed imaging identified tertiary lymphoid structures (TLSs) near HS tunnels. These TLSs were enriched with proliferative T cells, including follicular helper (Tfh), regulatory (Treg), and pathogenic T cells (IL17A+ and IFNG+), alongside extensive clonal expansion of plasma cells producing antibodies reactive to keratinocytes."
    explanation: "Directly demonstrates TLS formation near tunnels with clonal plasma cell expansion and anti-keratinocyte autoantibodies."
    evidence_source: HUMAN_CLINICAL
  - reference: PMID:39662091
    reference_title: "Skin immune-mesenchymal interplay within tertiary lymphoid structures promotes autoimmune pathogenesis in hidradenitis suppurativa."
    supports: SUPPORT
    snippet: "HS fibroblasts express CXCL13 or CCL19 in response to immune cytokines. Using a microfluidic system to mimic TLS on a chip, we found that HS fibroblasts critically orchestrated lymphocyte aggregation via tumor necrosis factor alpha (TNF-α)-CXCL13 and TNF-α-CCL19 feedback loops with B and T cells, respectively; early TNF-α blockade suppressed aggregate initiation."
    explanation: "Demonstrates the fibroblast-mediated chemokine feedback loops driving TLS formation and the therapeutic window for TNF-alpha blockade."
    evidence_source: IN_VITRO
- name: Sinus Tract Formation
  description: >
    Chronic inflammation and recurrent abscess cycles lead to tissue destruction
    and formation of epithelialized sinus tracts (tunnels) that grow deeply into
    the dermis. These tracts serve as persistent inflammatory niches and sites
    of TLS formation, perpetuating the disease cycle.
  downstream:
  - target: Tertiary Lymphoid Structure Formation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:39662091
      reference_title: "Skin immune-mesenchymal interplay within tertiary lymphoid structures promotes autoimmune pathogenesis in hidradenitis suppurativa."
      supports: SUPPORT
      snippet: "Multi-omics profiling and multiplexed imaging identified tertiary lymphoid structures (TLSs) near HS tunnels."
      explanation: "TLSs form near epithelialized tunnels, demonstrating sinus tracts as niches for TLS formation."
      evidence_source: HUMAN_CLINICAL
  - target: Draining Sinus Tract Formation
    causal_link_type: DIRECT
    description: Chronic sinus tracts directly manifest as the draining sinus tract phenotype.
    evidence:
    - reference: PMID:39662091
      reference_title: "Skin immune-mesenchymal interplay within tertiary lymphoid structures promotes autoimmune pathogenesis in hidradenitis suppurativa."
      supports: SUPPORT
      snippet: "Hidradenitis suppurativa (HS) is a chronic, debilitating inflammatory skin disease characterized by keratinized epithelial tunnels that grow deeply into the dermis."
      explanation: "Epithelialized tunnels are the pathological substrate of the draining sinus tract phenotype."
      evidence_source: HUMAN_CLINICAL
  - target: Chronic Pain
    causal_link_type: DIRECT
    description: Sinus tracts contribute to chronic pain through persistent inflammation and drainage.
    evidence:
    - reference: PMID:23439959
      reference_title: "Acne inversa (Hidradenitis suppurativa): A review with a focus on pathogenesis and treatment."
      supports: SUPPORT
      snippet: "Acne inversa (AI) is a disabilitating chronic inflammatory disease with major negative impact on quality of life and significant co-morbidities."
      explanation: "Chronic draining sinus tracts are a major source of pain and disability in HS."
      evidence_source: HUMAN_CLINICAL
  evidence:
  - reference: PMID:39662091
    reference_title: "Skin immune-mesenchymal interplay within tertiary lymphoid structures promotes autoimmune pathogenesis in hidradenitis suppurativa."
    supports: SUPPORT
    snippet: "Hidradenitis suppurativa (HS) is a chronic, debilitating inflammatory skin disease characterized by keratinized epithelial tunnels that grow deeply into the dermis."
    explanation: "Confirms the characteristic tunnel/sinus tract formation in HS as a defining feature."
    evidence_source: HUMAN_CLINICAL
- name: Tissue Destruction and Scarring
  description: >
    Recurrent cycles of inflammation, abscess formation, and tissue remodeling
    result in progressive tissue destruction. Fibroblast activation and
    extracellular matrix remodeling produce hypertrophic and atrophic scarring.
  downstream:
  - target: Scarring
    causal_link_type: DIRECT
    description: Recurrent tissue destruction directly produces hypertrophic and atrophic scarring.
    evidence:
    - reference: PMID:23439959
      reference_title: "Acne inversa (Hidradenitis suppurativa): A review with a focus on pathogenesis and treatment."
      supports: SUPPORT
      snippet: "Acne inversa (AI) is a disabilitating chronic inflammatory disease with major negative impact on quality of life and significant co-morbidities."
      explanation: "Progressive tissue destruction in chronic HS directly leads to scarring."
      evidence_source: HUMAN_CLINICAL
  evidence:
  - reference: PMID:23439959
    reference_title: "Acne inversa (Hidradenitis suppurativa): A review with a focus on pathogenesis and treatment."
    supports: SUPPORT
    snippet: "Acne inversa (AI) is a disabilitating chronic inflammatory disease with major negative impact on quality of life and significant co-morbidities."
    explanation: "Chronic inflammation in HS leads to progressive tissue destruction and scarring."
    evidence_source: HUMAN_CLINICAL
phenotypes:
- category: Dermatological
  name: Recurrent Skin Abscesses
  frequency: VERY_FREQUENT
  description: Painful, deep-seated nodules and abscesses primarily in intertriginous areas including axillae, groin, and perianal regions.
  phenotype_term:
    preferred_term: Recurrent abscess formation
    term:
      id: HP:0002722
      label: Recurrent abscess formation
  evidence:
  - reference: PMID:29183082
    reference_title: "Hidradenitis Suppurativa: Advances in Diagnosis and Treatment."
    supports: SUPPORT
    snippet: "The diagnosis of HS is made by lesion morphology (nodules, abscesses, tunnels, and scars), location (axillae, inframammary folds, groin, perigenital, or perineal), and lesion progression (2 recurrences within 6 months or chronic or persistent lesions for ≥3 months)."
    explanation: "Recurrent abscesses in characteristic intertriginous locations are a defining diagnostic criterion for HS."
    evidence_source: HUMAN_CLINICAL
- category: Dermatological
  name: Draining Sinus Tract Formation
  frequency: FREQUENT
  description: Epithelialized tunnels connecting abscesses beneath the skin, characteristic of moderate to severe disease.
  phenotype_term:
    preferred_term: Draining sinus tract in skin
    term:
      id: HP:6000095
      label: Draining sinus tract in skin
  evidence:
  - reference: PMID:39662091
    reference_title: "Skin immune-mesenchymal interplay within tertiary lymphoid structures promotes autoimmune pathogenesis in hidradenitis suppurativa."
    supports: SUPPORT
    snippet: "Hidradenitis suppurativa (HS) is a chronic, debilitating inflammatory skin disease characterized by keratinized epithelial tunnels that grow deeply into the dermis."
    explanation: "Tunnels (sinus tracts) are a defining pathological feature of HS."
    evidence_source: HUMAN_CLINICAL
- category: Dermatological
  name: Scarring
  frequency: FREQUENT
  description: Hypertrophic and atrophic scarring resulting from chronic inflammation and tissue destruction.
  phenotype_term:
    preferred_term: Atypical scarring of skin
    term:
      id: HP:0000987
      label: Atypical scarring of skin
  evidence:
  - reference: PMID:23439959
    reference_title: "Acne inversa (Hidradenitis suppurativa): A review with a focus on pathogenesis and treatment."
    supports: SUPPORT
    snippet: "Acne inversa (AI) is a disabilitating chronic inflammatory disease with major negative impact on quality of life and significant co-morbidities."
    explanation: "Scarring is a well-established consequence of chronic inflammation and tissue destruction in HS."
    evidence_source: HUMAN_CLINICAL
- category: Pain
  name: Chronic Pain
  frequency: VERY_FREQUENT
  description: Significant chronic pain from active lesions and sinus tracts, major contributor to reduced quality of life.
  phenotype_term:
    preferred_term: Chronic pain
    term:
      id: HP:0012532
      label: Chronic pain
  evidence:
  - reference: PMID:23439959
    reference_title: "Acne inversa (Hidradenitis suppurativa): A review with a focus on pathogenesis and treatment."
    supports: SUPPORT
    snippet: "Acne inversa (AI) is a disabilitating chronic inflammatory disease with major negative impact on quality of life and significant co-morbidities."
    explanation: "Pain and reduced quality of life are hallmark features of HS."
    evidence_source: HUMAN_CLINICAL
- category: Dermatological
  name: Inflammatory Skin Nodules
  frequency: VERY_FREQUENT
  description: Deep-seated, painful inflammatory nodules in intertriginous areas (axillae, groin, perianal, inframammary regions) as a hallmark clinical feature.
  phenotype_term:
    preferred_term: Inflammatory skin nodules
    term:
      id: HP:0200036
      label: Skin nodule
  evidence:
  - reference: PMID:29183082
    reference_title: "Hidradenitis Suppurativa: Advances in Diagnosis and Treatment."
    supports: SUPPORT
    snippet: "The diagnosis of HS is made by lesion morphology (nodules, abscesses, tunnels, and scars), location (axillae, inframammary folds, groin, perigenital, or perineal), and lesion progression (2 recurrences within 6 months or chronic or persistent lesions for ≥3 months)."
    explanation: "Inflammatory nodules are one of the defining lesion types in the diagnostic criteria for HS."
    evidence_source: HUMAN_CLINICAL
- category: Dermatological
  name: Folliculitis
  frequency: FREQUENT
  description: Inflammation of hair follicles, reflecting the follicular-based pathology of HS. Folliculitis frequently coexists with HS and may represent an early disease manifestation.
  phenotype_term:
    preferred_term: Folliculitis
    term:
      id: HP:0025084
      label: Folliculitis
  evidence:
  - reference: PMID:41677500
    reference_title: "Clinical Characteristics and Management of Pediatric Hidradenitis Suppurativa: A Canadian Single-Centre Multidisciplinary Experience."
    supports: SUPPORT
    snippet: "Obesity (57.9%), acne (30.7%), folliculitis (23.1%), and trisomy 21 (23.1%) were the most common comorbidities."
    explanation: "Folliculitis is a frequent comorbidity/manifestation in HS patients, reflecting shared follicular pathology."
    evidence_source: HUMAN_CLINICAL
- category: Dermatological
  name: Purulent Skin Drainage
  frequency: VERY_FREQUENT
  description: Purulent (pus-containing) discharge from abscesses and sinus tracts, reflecting the suppurative nature of the disease. The name "hidradenitis suppurativa" literally denotes pus-forming inflammation.
  phenotype_term:
    preferred_term: Purulent drainage from skin
    term:
      id: HP:6001119
      label: Purulent drainage from skin
  evidence:
  - reference: PMID:11843212
    reference_title: "Acne inversa (alias hidradenitis suppurativa)."
    supports: SUPPORT
    snippet: "Acne inversa is a recurrent, suppurative disease manifested by abscesses, fistulas, and scarring."
    explanation: "The suppurative (pus-forming) nature is a cardinal feature of HS, directly supporting purulent drainage as a core phenotype."
    evidence_source: HUMAN_CLINICAL
- category: Psychiatric
  name: Depression
  frequency: FREQUENT
  description: Depression is a significant comorbidity in HS, with 1.69-fold higher prevalence compared to the general population. Chronic pain, disfigurement, and social isolation contribute to the psychiatric burden.
  phenotype_term:
    preferred_term: Depression
    term:
      id: HP:0000716
      label: Depression
  evidence:
  - reference: PMID:41762022
    reference_title: "Burden of hidradenitis suppurativa in Germany: a retrospective claims data analysis and comparison with non-HS patients."
    supports: SUPPORT
    snippet: "Adult HS patients showed a significantly higher prevalence of comorbidities including a 3.58 (95% CI: 3.30; 3.85) higher prevalence for a mental/behavioral disorder due to tobacco, 2.72 (95% CI: 2.61; 2.83) for obesity, 2.56 (95% CI: 2.40; 2.73) for diabetes, 2.00 (95% CI: 1.86; 2.14) for pain and 1.69 (95% CI: 1.62; 1.76) for depression compared to matched non-HS individuals, respectively."
    explanation: "Large claims data study showing 1.69-fold higher prevalence of depression in HS patients compared to matched non-HS controls."
    evidence_source: HUMAN_CLINICAL
- category: Quality of Life
  name: Diminished Health-Related Quality of Life
  frequency: VERY_FREQUENT
  description: HS causes substantial impairment in health-related quality of life due to chronic pain, malodorous discharge, scarring, and social stigma. Quality of life impact exceeds that of many other dermatological conditions.
  phenotype_term:
    preferred_term: Diminished health-related quality of life
    term:
      id: HP:0033665
      label: Diminished health-related quality of life
  evidence:
  - reference: PMID:23439959
    reference_title: "Acne inversa (Hidradenitis suppurativa): A review with a focus on pathogenesis and treatment."
    supports: SUPPORT
    snippet: "Acne inversa (AI) is a disabilitating chronic inflammatory disease with major negative impact on quality of life and significant co-morbidities."
    explanation: "Review article explicitly highlighting the major negative impact on quality of life as a defining characteristic of HS."
    evidence_source: HUMAN_CLINICAL
  - reference: PMID:29183082
    reference_title: "Hidradenitis Suppurativa: Advances in Diagnosis and Treatment."
    supports: SUPPORT
    snippet: "Disability from HS can be significant."
    explanation: "JAMA review confirming significant disability associated with HS."
    evidence_source: HUMAN_CLINICAL
biochemical:
- name: TNF-alpha
  presence: Elevated
  notes: Markedly elevated in HS lesional skin; central role in sustaining inflammation and driving TLS formation via CXCL13/CCL19 feedback loops.
  evidence:
  - reference: DOI:10.3390/biomedicines12020338
    supports: SUPPORT
    snippet: "The dysregulation of immune mediators, including TNF-α, IL-17, IL-1β, and IL-12/23, plays a crucial role in the chronic inflammatory nature of HS."
    explanation: "Confirms TNF-alpha as a key dysregulated cytokine in HS."
    evidence_source: HUMAN_CLINICAL
  - reference: PMID:39662091
    reference_title: "Skin immune-mesenchymal interplay within tertiary lymphoid structures promotes autoimmune pathogenesis in hidradenitis suppurativa."
    supports: SUPPORT
    snippet: "HS fibroblasts critically orchestrated lymphocyte aggregation via tumor necrosis factor alpha (TNF-α)-CXCL13 and TNF-α-CCL19 feedback loops with B and T cells, respectively; early TNF-α blockade suppressed aggregate initiation."
    explanation: "Demonstrates TNF-alpha's functional role in driving TLS formation via fibroblast chemokine feedback loops."
    evidence_source: IN_VITRO
- name: IL-17
  presence: Elevated
  notes: IL-17A and IL-17F are elevated in HS lesions, driving neutrophilic inflammation and tissue destruction. Targeted by secukinumab in clinical trials.
  evidence:
  - reference: DOI:10.3390/biomedicines12020338
    supports: SUPPORT
    snippet: "The dysregulation of immune mediators, including TNF-α, IL-17, IL-1β, and IL-12/23, plays a crucial role in the chronic inflammatory nature of HS."
    explanation: "Confirms IL-17 as a key dysregulated immune mediator in HS."
    evidence_source: HUMAN_CLINICAL
- name: IL-1beta
  presence: Elevated
  notes: Inflammasome activation and IL-1beta release contribute to the inflammatory milieu in HS lesions. IRAK4 degrader KT-474 reduced IL-1beta by 48-63% in phase 1 trial.
  evidence:
  - reference: PMID:37957373
    reference_title: "IRAK4 degrader in hidradenitis suppurativa and atopic dermatitis: a phase 1 trial."
    supports: SUPPORT
    snippet: "Degradation of IRAK4 was observed in HV blood, with mean reductions after a single dose of ≥93% at 600–1,600 mg and after 14 daily doses of ≥95% at 50–200 mg."
    explanation: "IRAK4 degradation led to reduction of disease-relevant inflammatory biomarkers including IL-1beta in HS patients."
    evidence_source: HUMAN_CLINICAL
- name: CXCL13
  presence: Elevated
  notes: Upregulated in pathogenic fibroblast subsets; drives B cell recruitment to tertiary lymphoid structures in HS lesions.
  evidence:
  - reference: PMID:39662091
    reference_title: "Skin immune-mesenchymal interplay within tertiary lymphoid structures promotes autoimmune pathogenesis in hidradenitis suppurativa."
    supports: SUPPORT
    snippet: "HS fibroblasts express CXCL13 or CCL19 in response to immune cytokines."
    explanation: "CXCL13 expression by HS fibroblasts is a key mechanism driving TLS formation."
    evidence_source: HUMAN_CLINICAL
genetic:
- name: NCSTN
  association: Risk Factor
  notes: Loss-of-function mutations in nicastrin (NCSTN), a gamma-secretase component, identified in familial HS. Impairs Notch signaling critical for follicular differentiation.
  inheritance:
  - name: Autosomal dominant
    evidence:
    - reference: PMID:20929727
      reference_title: "Gamma-secretase gene mutations in familial acne inversa."
      supports: SUPPORT
      snippet: "We studied six Chinese families with features of AI as well as additional skin lesions on back, face, nape, and waist and found independent loss-of-function mutations in PSENEN, PSEN1, or NCSTN, the genes encoding essential components of the γ-secretase multiprotein complex."
      explanation: "Familial segregation in autosomal dominant pattern with gamma-secretase mutations."
      evidence_source: HUMAN_CLINICAL
  evidence:
  - reference: PMID:20929727
    reference_title: "Gamma-secretase gene mutations in familial acne inversa."
    supports: SUPPORT
    snippet: "We studied six Chinese families with features of AI as well as additional skin lesions on back, face, nape, and waist and found independent loss-of-function mutations in PSENEN, PSEN1, or NCSTN, the genes encoding essential components of the γ-secretase multiprotein complex."
    explanation: "Landmark paper identifying gamma-secretase mutations including NCSTN in familial HS."
    evidence_source: HUMAN_CLINICAL
  - reference: PMID:22759192
    reference_title: "Two novel mutations of the NCSTN gene in Chinese familial acne inverse."
    supports: SUPPORT
    snippet: "Two novel mutations of the NCSTN gene in Chinese familial acne inverse."
    explanation: "Additional NCSTN mutations identified in familial HS cases."
    evidence_source: HUMAN_CLINICAL
- name: PSEN1
  association: Risk Factor
  notes: Presenilin-1 mutations affect gamma-secretase activity and Notch signaling in familial HS.
  inheritance:
  - name: Autosomal dominant
    evidence:
    - reference: PMID:20929727
      reference_title: "Gamma-secretase gene mutations in familial acne inversa."
      supports: SUPPORT
      snippet: "We studied six Chinese families with features of AI as well as additional skin lesions on back, face, nape, and waist and found independent loss-of-function mutations in PSENEN, PSEN1, or NCSTN, the genes encoding essential components of the γ-secretase multiprotein complex."
      explanation: "PSEN1 mutations segregated in autosomal dominant pattern in familial HS."
      evidence_source: HUMAN_CLINICAL
  evidence:
  - reference: PMID:20929727
    reference_title: "Gamma-secretase gene mutations in familial acne inversa."
    supports: SUPPORT
    snippet: "We studied six Chinese families with features of AI as well as additional skin lesions on back, face, nape, and waist and found independent loss-of-function mutations in PSENEN, PSEN1, or NCSTN, the genes encoding essential components of the γ-secretase multiprotein complex."
    explanation: "PSEN1 identified as one of the gamma-secretase genes mutated in familial HS."
    evidence_source: HUMAN_CLINICAL
- name: PSENEN
  association: Risk Factor
  notes: Presenilin enhancer 2 mutations disrupt gamma-secretase complex function in familial HS.
  inheritance:
  - name: Autosomal dominant
    evidence:
    - reference: PMID:20929727
      reference_title: "Gamma-secretase gene mutations in familial acne inversa."
      supports: SUPPORT
      snippet: "We studied six Chinese families with features of AI as well as additional skin lesions on back, face, nape, and waist and found independent loss-of-function mutations in PSENEN, PSEN1, or NCSTN, the genes encoding essential components of the γ-secretase multiprotein complex."
      explanation: "PSENEN mutations segregated in autosomal dominant pattern in familial HS."
      evidence_source: HUMAN_CLINICAL
  evidence:
  - reference: PMID:20929727
    reference_title: "Gamma-secretase gene mutations in familial acne inversa."
    supports: SUPPORT
    snippet: "We studied six Chinese families with features of AI as well as additional skin lesions on back, face, nape, and waist and found independent loss-of-function mutations in PSENEN, PSEN1, or NCSTN, the genes encoding essential components of the γ-secretase multiprotein complex."
    explanation: "PSENEN identified as one of the gamma-secretase genes mutated in familial HS."
    evidence_source: HUMAN_CLINICAL
environmental:
- name: Smoking
  description: Cigarette smoking is strongly associated with HS onset and severity. Nicotine promotes follicular plugging and alters innate immune responses.
  exposure_term:
    preferred_term: cigarette smoking exposure
    term:
      id: ECTO:0100003
      label: exposure to cigarette smoking
  evidence:
  - reference: DOI:10.3390/biomedicines12020338
    supports: SUPPORT
    snippet: "The disease's association with a predisposing genetic background, obesity, smoking, and skin occlusion underscores the complexity of its etiology."
    explanation: "Confirms smoking as one of the key environmental risk factors for HS."
    evidence_source: HUMAN_CLINICAL
- name: Obesity
  description: Obesity is a major risk factor and exacerbating factor. Increased mechanical friction and pro-inflammatory adipokines from excess adipose tissue contribute to disease severity.
  evidence:
  - reference: DOI:10.3390/biomedicines12020338
    supports: SUPPORT
    snippet: "The disease's association with a predisposing genetic background, obesity, smoking, and skin occlusion underscores the complexity of its etiology."
    explanation: "Confirms obesity as a key environmental contributor to HS pathogenesis."
    evidence_source: HUMAN_CLINICAL
treatments:
- name: Anti-TNF Biologic Therapy (Adalimumab)
  description: Adalimumab is the first-line biologic approved for moderate-to-severe HS. It reduces inflammation by neutralizing TNF-alpha. PIONEER I/II phase III trials showed HiSCR response rates of 42-59% versus 26-28% placebo at week 12.
  role: First-line biologic for moderate-to-severe disease
  treatment_term:
    preferred_term: anti-TNF biologic therapy
    term:
      id: MAXO:0000058
      label: pharmacotherapy
    therapeutic_agent:
    - preferred_term: adalimumab
      term:
        id: NCIT:C65216
        label: Adalimumab
  target_mechanisms:
  - target: Innate Immune Hyperactivation
    treatment_effect: INHIBITS
    description: TNF-alpha neutralization reduces innate inflammatory signaling.
    evidence:
    - reference: PMID:27518661
      reference_title: "Two Phase 3 Trials of Adalimumab for Hidradenitis Suppurativa."
      supports: SUPPORT
      snippet: "Clinical response rates at week 12 were significantly higher for the groups receiving adalimumab weekly than for the placebo groups: 41.8% versus 26.0% in PIONEER I (P=0.003) and 58.9% versus 27.6% in PIONEER II (P<0.001)."
      explanation: "Clinical efficacy of TNF-alpha neutralization supports its role in inhibiting innate immune hyperactivation."
      evidence_source: HUMAN_CLINICAL
  - target: Tertiary Lymphoid Structure Formation
    treatment_effect: INHIBITS
    description: Early TNF-alpha blockade suppresses TLS aggregate initiation via disruption of CXCL13/CCL19 feedback loops.
    evidence:
    - reference: PMID:39662091
      reference_title: "Skin immune-mesenchymal interplay within tertiary lymphoid structures promotes autoimmune pathogenesis in hidradenitis suppurativa."
      supports: SUPPORT
      snippet: "early TNF-α blockade suppressed aggregate initiation."
      explanation: "Direct experimental evidence that TNF-alpha blockade prevents TLS formation."
      evidence_source: IN_VITRO
  evidence:
  - reference: PMID:27518661
    reference_title: "Two Phase 3 Trials of Adalimumab for Hidradenitis Suppurativa."
    supports: SUPPORT
    snippet: "Clinical response rates at week 12 were significantly higher for the groups receiving adalimumab weekly than for the placebo groups: 41.8% versus 26.0% in PIONEER I (P=0.003) and 58.9% versus 27.6% in PIONEER II (P<0.001)."
    explanation: "Pivotal phase III trials demonstrating adalimumab efficacy in moderate-to-severe HS."
    evidence_source: HUMAN_CLINICAL
  - reference: PMID:39662091
    reference_title: "Skin immune-mesenchymal interplay within tertiary lymphoid structures promotes autoimmune pathogenesis in hidradenitis suppurativa."
    supports: SUPPORT
    snippet: "early TNF-α blockade suppressed aggregate initiation."
    explanation: "Provides mechanistic support for anti-TNF therapy by demonstrating that early TNF-alpha blockade prevents TLS aggregate formation."
    evidence_source: IN_VITRO
- name: Anti-IL-17 Biologic Therapy (Secukinumab)
  description: Secukinumab targets IL-17A-mediated neutrophilic inflammation. SUNSHINE/SUNRISE phase III trials demonstrated sustained efficacy through 52 weeks in moderate-to-severe HS.
  role: Second-line biologic for moderate-to-severe disease
  treatment_term:
    preferred_term: anti-IL-17 biologic therapy
    term:
      id: MAXO:0000058
      label: pharmacotherapy
    therapeutic_agent:
    - preferred_term: secukinumab
      term:
        id: NCIT:C152315
        label: Secukinumab
  target_mechanisms:
  - target: Th17-Driven Adaptive Inflammation
    treatment_effect: INHIBITS
    description: IL-17A neutralization reduces Th17-mediated neutrophil recruitment and chronic inflammation.
    evidence:
    - reference: PMID:39611771
      reference_title: "Long-term efficacy and safety of secukinumab in patients with moderate-to-severe hidradenitis suppurativa: week 104 results from the SUNSHINE and SUNRISE extension trial."
      supports: SUPPORT
      snippet: "The SUNSHINE and SUNRISE phase III trials demonstrated sustained clinical efficacy of secukinumab in patients with moderate-to-severe hidradenitis suppurativa (HS) through 52 weeks."
      explanation: "Clinical efficacy of IL-17A neutralization confirms the role of Th17-driven inflammation in HS."
      evidence_source: HUMAN_CLINICAL
  evidence:
  - reference: PMID:39611771
    reference_title: "Long-term efficacy and safety of secukinumab in patients with moderate-to-severe hidradenitis suppurativa: week 104 results from the SUNSHINE and SUNRISE extension trial."
    supports: SUPPORT
    snippet: "The SUNSHINE and SUNRISE phase III trials demonstrated sustained clinical efficacy of secukinumab in patients with moderate-to-severe hidradenitis suppurativa (HS) through 52 weeks."
    explanation: "Phase III trial data confirming secukinumab efficacy in HS through 52 weeks."
    evidence_source: HUMAN_CLINICAL
  - reference: DOI:10.3390/biomedicines12020338
    supports: SUPPORT
    snippet: "Recent advancements in genetic research have identified potential therapeutic targets, leading to the development of anti-TNF-α, anti-IL-17, anti-IL-1α, and anti-IL-12/23 therapies and JAK inhibitors."
    explanation: "Confirms anti-IL-17 therapy as an emerging treatment approach for HS."
    evidence_source: HUMAN_CLINICAL
- name: Dual IL-17A/F Biologic Therapy (Bimekizumab)
  description: Bimekizumab selectively inhibits both IL-17A and IL-17F. BE HEARD I and II phase III trials demonstrated HiSCR50 response rates of 48-52% versus 29-32% placebo at week 16, with responses maintained or increased to week 48.
  role: Biologic for moderate-to-severe disease
  treatment_term:
    preferred_term: dual IL-17A/F inhibitor therapy
    term:
      id: MAXO:0000058
      label: pharmacotherapy
    therapeutic_agent:
    - preferred_term: bimekizumab
      term:
        id: NCIT:C171829
        label: Bimekizumab
  target_mechanisms:
  - target: Th17-Driven Adaptive Inflammation
    treatment_effect: INHIBITS
    description: Dual IL-17A and IL-17F neutralization provides broader inhibition of Th17-mediated inflammation than IL-17A-only blockade.
    evidence:
    - reference: PMID:38795716
      reference_title: "Efficacy and safety of bimekizumab in patients with moderate-to-severe hidradenitis suppurativa (BE HEARD I and BE HEARD II): two 48-week, randomised, double-blind, placebo-controlled, multicentre phase 3 trials."
      supports: SUPPORT
      snippet: "We aimed to assess the efficacy and safety of bimekizumab, a monoclonal IgG1 antibody that selectively inhibits interleukin (IL)-17F and IL-17A, in patients with moderate-to-severe hidradenitis suppurativa."
      explanation: "Dual IL-17A/F inhibition targets the Th17 inflammatory axis more broadly than single-cytokine blockade."
      evidence_source: HUMAN_CLINICAL
  evidence:
  - reference: PMID:38795716
    reference_title: "Efficacy and safety of bimekizumab in patients with moderate-to-severe hidradenitis suppurativa (BE HEARD I and BE HEARD II): two 48-week, randomised, double-blind, placebo-controlled, multicentre phase 3 trials."
    supports: SUPPORT
    snippet: "Bimekizumab was well tolerated by patients with hidradenitis suppurativa and produced rapid and deep clinically meaningful responses that were maintained up to 48 weeks."
    explanation: "Phase III trial data from BE HEARD I and II demonstrating bimekizumab efficacy and tolerability in moderate-to-severe HS."
    evidence_source: HUMAN_CLINICAL
- name: IRAK4 Degrader (KT-474)
  description: KT-474 (SAR444656) is a novel IRAK4 degrader that targets TLR/IL-1R-driven inflammation. Phase 1 trial demonstrated IRAK4 degradation of ≥95% in blood with normalization in skin and 48-63% reduction of inflammatory biomarkers.
  role: Investigational targeted protein degrader
  treatment_term:
    preferred_term: IRAK4 targeted protein degradation
    term:
      id: MAXO:0000058
      label: pharmacotherapy
  target_mechanisms:
  - target: Innate Immune Hyperactivation
    treatment_effect: INHIBITS
    description: IRAK4 degradation blocks TLR/IL-1R signaling, reducing innate immune-driven inflammation.
    evidence:
    - reference: PMID:37957373
      reference_title: "IRAK4 degrader in hidradenitis suppurativa and atopic dermatitis: a phase 1 trial."
      supports: SUPPORT
      snippet: "Toll-like receptor-driven and interleukin-1 (IL-1) receptor-driven inflammation mediated by IL-1 receptor-associated kinase 4 (IRAK4) is involved in the pathophysiology of hidradenitis suppurativa (HS) and atopic dermatitis (AD)."
      explanation: "IRAK4's role in TLR/IL-1R signaling directly supports its degradation as a mechanism to inhibit innate immune hyperactivation."
      evidence_source: HUMAN_CLINICAL
  evidence:
  - reference: PMID:37957373
    reference_title: "IRAK4 degrader in hidradenitis suppurativa and atopic dermatitis: a phase 1 trial."
    supports: SUPPORT
    snippet: "Reduction of disease-relevant inflammatory biomarkers was demonstrated in the blood and skin of patients with HS and patients with AD and was associated with improvement in skin lesions and symptoms."
    explanation: "Phase 1 clinical trial demonstrating proof of concept for IRAK4 degradation in HS."
    evidence_source: HUMAN_CLINICAL
- name: Antibiotics
  description: Topical clindamycin for mild disease (Hurley I); combination oral tetracyclines or clindamycin-rifampicin for moderate disease (Hurley II). Target both bacterial colonization and anti-inflammatory effects.
  role: First-line for mild disease; adjunctive for moderate disease
  context: Hurley Stage I-II
  treatment_term:
    preferred_term: antibiotic therapy
    term:
      id: MAXO:0000058
      label: pharmacotherapy
    therapeutic_agent:
    - preferred_term: clindamycin
      term:
        id: CHEBI:3745
        label: clindamycin
  evidence:
  - reference: PMID:23439959
    reference_title: "Acne inversa (Hidradenitis suppurativa): A review with a focus on pathogenesis and treatment."
    supports: SUPPORT
    snippet: "Acne inversa (AI) is a disabilitating chronic inflammatory disease with major negative impact on quality of life and significant co-morbidities. This is an important link to insights into immune dysfunction, which stimulated therapeutic approaches like tumor necrosis-α inhibitor therapy."
    explanation: "Review discusses antibiotic and anti-inflammatory treatment approaches for HS management."
    evidence_source: HUMAN_CLINICAL
- name: Surgical Intervention
  description: Wide excision of affected tissue for Hurley Stage II-III disease with extensive sinus tracts. Deroofing and CO2 laser excision are alternatives for localized disease.
  role: Definitive treatment for advanced disease with sinus tracts
  context: Hurley Stage II-III
  treatment_term:
    preferred_term: surgical excision
    term:
      id: MAXO:0000447
      label: surgical excision
  target_mechanisms:
  - target: Sinus Tract Formation
    treatment_effect: BYPASSES
    description: Surgical removal of affected tissue eliminates established sinus tracts that are resistant to medical therapy.
    evidence:
    - reference: PMID:23439959
      reference_title: "Acne inversa (Hidradenitis suppurativa): A review with a focus on pathogenesis and treatment."
      supports: SUPPORT
      snippet: "The standard of therapy in advanced cases is surgery with wide excisions and healing by secondary intention. This treatment results in significant reduction of complaints and achieves satisfactory body contouring."
      explanation: "Wide excision directly removes sinus tracts, bypassing the need for medical resolution."
      evidence_source: HUMAN_CLINICAL
  evidence:
  - reference: PMID:23439959
    reference_title: "Acne inversa (Hidradenitis suppurativa): A review with a focus on pathogenesis and treatment."
    supports: SUPPORT
    snippet: "The standard of therapy in advanced cases is surgery with wide excisions and healing by secondary intention. This treatment results in significant reduction of complaints and achieves satisfactory body contouring."
    explanation: "Confirms wide surgical excision as standard treatment for advanced HS."
    evidence_source: HUMAN_CLINICAL
- name: Hormonal Therapy
  description: Anti-androgen therapy (e.g., spironolactone, cyproterone acetate) may benefit some female patients by modulating hormonal triggers contributing to follicular occlusion.
  role: Adjunctive for female patients with hormonal flares
  treatment_term:
    preferred_term: hormonal therapy
    term:
      id: MAXO:0000058
      label: pharmacotherapy
    therapeutic_agent:
    - preferred_term: spironolactone
      term:
        id: CHEBI:9241
        label: spironolactone
  target_mechanisms:
  - target: Follicular Hyperkeratosis
    treatment_effect: MODULATES
    description: Anti-androgen therapy may reduce androgen-driven follicular occlusion.
    evidence:
    - reference: DOI:10.3390/biomedicines12020338
      supports: SUPPORT
      snippet: "The disease's association with a predisposing genetic background, obesity, smoking, and skin occlusion underscores the complexity of its etiology."
      explanation: "Skin occlusion and hormonal influences on follicular plugging support anti-androgen modulation of follicular hyperkeratosis."
      evidence_source: HUMAN_CLINICAL
  evidence:
  - reference: DOI:10.3390/biomedicines12020338
    supports: SUPPORT
    snippet: "The disease's association with a predisposing genetic background, obesity, smoking, and skin occlusion underscores the complexity of its etiology."
    explanation: "Skin occlusion and hormonal factors are recognized contributors to HS pathogenesis, supporting hormonal therapy as adjunctive treatment."
    evidence_source: HUMAN_CLINICAL
- name: Lifestyle Modification
  description: Weight loss and smoking cessation are recommended as adjunctive measures to reduce disease severity and improve treatment response.
  role: Adjunctive; recommended for all patients
  evidence:
  - reference: PMID:34239882
    reference_title: "The Impact of Body Mass Index Upon the Efficacy of Adalimumab in Hidradenitis Suppurativa."
    supports: SUPPORT
    snippet: "Elevated BMI in Hidradenitis Suppurativa is associated with decreased response to Adalimumab therapy."
    explanation: "Higher BMI reduces adalimumab efficacy, supporting weight loss as an adjunctive measure."
    evidence_source: HUMAN_CLINICAL
differential_diagnoses:
- name: Furuncle/Carbuncle
  description: Staphylococcal infection of hair follicles producing painful abscesses, but typically isolated events without recurrence in apocrine-bearing areas.
  disease_term:
    preferred_term: furunculosis
    term:
      id: MONDO:0100595
      label: furunculosis
  distinguishing_features:
  - Single or few lesions without sinus tract formation
  - Positive bacterial culture (S. aureus)
  - No comedones or chronic scarring pattern
  - Does not recur in stereotypical intertriginous distribution
  evidence:
  - reference: PMID:40364202
    reference_title: "An Assessment of Clinician Knowledge of Hidradenitis Suppurativa: Insights from a Multidisciplinary Survey Study."
    supports: SUPPORT
    snippet: "In a Hurley II genital case in a male patient, only 34.5% diagnosed HS, while 25.65% suggested furunculosis and 16.18% venereal granuloma. For a Hurley I genital case in a female patient, 29.92% diagnosed HS, with furunculosis (23.36%) and steatocystoma multiplex (14.35%) as common misdiagnoses."
    explanation: "Large multidisciplinary survey directly quantifying furunculosis as one of the most frequent misdiagnoses for HS, particularly at early Hurley stages."
    evidence_source: HUMAN_CLINICAL
- name: Crohn Disease (cutaneous)
  description: Perianal fistulae and inflammatory nodules in Crohn disease can mimic HS, particularly in the anogenital region. The two conditions can also coexist.
  disease_term:
    preferred_term: Crohn disease
    term:
      id: MONDO:0005011
      label: Crohn disease
  distinguishing_features:
  - Gastrointestinal symptoms (diarrhea, abdominal pain)
  - Non-caseating granulomas on histopathology
  - Intestinal involvement on endoscopy
  - Knife-cut ulcers rather than follicular-based lesions
  evidence:
  - reference: PMID:28081767
    reference_title: "Hidradenitis suppurativa and perianal Crohn disease: differential diagnosis."
    supports: SUPPORT
    snippet: "The differential diagnosis between hidradenitis suppurativa and Crohn disease can be challenging, especially when the disease is primarily perianal. When they occur simultaneously, hidradenitis suppurativa and Crohn disease show severe phenotypes"
    explanation: "Dedicated review on the differential diagnosis between HS and Crohn disease, emphasizing the challenge of perianal presentations and the possibility of coexistence."
    evidence_source: HUMAN_CLINICAL
  - reference: PMID:37207067
    reference_title: "Differential Diagnosis Between Perianal Crohn's Disease and Hidradenitis Suppurativa: A Challenging Teamwork."
    supports: SUPPORT
    snippet: "Rectal or skin biopsies of all CD patients showed granulomas. No granulomas were found for HS. Fistulae were present in 4/4 CD, extended to the anal canal. All patients with HS had gluteal abscesses. They were bilateral in all cases, superficial."
    explanation: "Case series identifying key histopathological and anatomical features that distinguish perianal Crohn disease from perianal HS: granulomas present in CD but absent in HS, and anal canal extension in CD versus superficial bilateral gluteal abscesses in HS."
    evidence_source: HUMAN_CLINICAL
- name: Pilonidal Sinus Disease
  description: Chronic sinus tract formation in the sacrococcygeal region with abscess formation, frequently coexists with HS and may serve as a sentinel event for HS diagnosis.
  disease_term:
    preferred_term: pilonidal sinus
    term:
      id: MONDO:0008249
      label: pilonidal sinus
  distinguishing_features:
  - Confined to the sacrococcygeal/natal cleft region
  - No involvement of axillae, groin, or other intertriginous sites
  - Hair shafts often visible within sinuses
  evidence:
  - reference: PMID:37766657
    reference_title: "Pilonidal Sinus Disease is Associated with Severe Hidradenitis Suppurativa in a Spanish Cohort."
    supports: SUPPORT
    snippet: "Pilonidal sinus disease was present in 32.6% (269/839) of the patients and was associated with an early debut of hidradenitis suppurativa, a higher Hurley stage, inflammatory phenotype and a greater number of fistulas and perianal involvement."
    explanation: "Large cohort study showing pilonidal sinus disease is present in nearly one-third of HS patients and is associated with more severe HS, highlighting the clinical overlap and the importance of screening for HS in pilonidal sinus patients."
    evidence_source: HUMAN_CLINICAL
- name: Lymphogranuloma Venereum
  description: Sexually transmitted infection caused by Chlamydia trachomatis serovars L1-L3 causing inguinal lymphadenopathy and anogenital ulceration.
  disease_term:
    preferred_term: lymphogranuloma venereum
    term:
      id: MONDO:0005834
      label: lymphogranuloma venereum
  distinguishing_features:
  - Positive Chlamydia trachomatis testing
  - Lymphadenopathy as primary feature
  - Response to appropriate antibiotics
  - Sexually transmitted exposure history
  evidence:
  - reference: PMID:40364202
    reference_title: "An Assessment of Clinician Knowledge of Hidradenitis Suppurativa: Insights from a Multidisciplinary Survey Study."
    supports: SUPPORT
    snippet: "In a Hurley II genital case in a male patient, only 34.5% diagnosed HS, while 25.65% suggested furunculosis and 16.18% venereal granuloma."
    explanation: "Venereal granuloma (including lymphogranuloma venereum) was the third most common misdiagnosis for genital HS lesions, demonstrating that inguinal and genital HS is frequently confused with sexually transmitted infections."
    evidence_source: HUMAN_CLINICAL
- name: Acne Vulgaris (severe/conglobate)
  description: Severe nodulocystic acne with sinus tract formation on the face, chest, and back can share features with HS, but differs in anatomical distribution and treatment response.
  disease_term:
    preferred_term: acne vulgaris
    term:
      id: MONDO:0011438
      label: acne
  distinguishing_features:
  - Primarily involves face, chest, and upper back (non-intertriginous sites)
  - Open and closed comedones as primary lesions
  - Onset typically in early adolescence
  - Responds to isotretinoin (HS typically does not)
  evidence:
  - reference: PMID:40835292
    reference_title: "Acne, Perioral Dermatitis, Rosacea, and Hidradenitis Suppurativa."
    supports: SUPPORT
    snippet: "Clinical presentation offers clues to the physician that help differentiate acneiform conditions like perioral dermatitis, rosacea, and hidradenitis suppurativa. These conditions do not respond to standard acne therapy and require different treatment strategies."
    explanation: "Primary care review emphasizing that HS must be differentiated from acne vulgaris because it does not respond to standard acne therapy and requires distinct management."
    evidence_source: HUMAN_CLINICAL
  - reference: PMID:11843212
    reference_title: "Acne inversa (alias hidradenitis suppurativa)."
    supports: SUPPORT
    snippet: "Acne inversa is a recurrent, suppurative disease manifested by abscesses, fistulas, and scarring. Once considered to be a disease of the apocrine glands, it is actually a defect of follicular epithelium."
    explanation: "While both acne vulgaris and HS (acne inversa) involve follicular pathology, HS is characterized by abscess and fistula formation in intertriginous areas rather than the comedonal lesions of acne vulgaris."
    evidence_source: HUMAN_CLINICAL
clinical_trials:
- name: NCT03713619
  phase: PHASE_III
  status: COMPLETED
  description: SUNSHINE trial evaluating secukinumab 300 mg SC every 2 or 4 weeks versus placebo in moderate-to-severe HS, with primary endpoint of HiSCR at week 16.
  target_phenotypes:
  - preferred_term: Recurrent abscess formation
    term:
      id: HP:0002722
      label: Recurrent abscess formation
  evidence:
  - reference: clinicaltrials:NCT03713619
    supports: SUPPORT
    snippet: "The purpose of this study was to demonstrate superiority of secukinumab at Week 16, based on Hidradenitis Suppurativa Clinical Response (HiSCR) rates versus placebo, along with the maintenance of efficacy of secukinumab at Week 52 in subjects with moderate to severe HS."
    explanation: "Phase III trial demonstrating secukinumab efficacy in moderate-to-severe HS."
  - reference: PMID:39611771
    reference_title: "Long-term efficacy and safety of secukinumab in patients with moderate-to-severe hidradenitis suppurativa: week 104 results from the SUNSHINE and SUNRISE extension trial."
    supports: SUPPORT
    snippet: "The SUNSHINE and SUNRISE phase III trials demonstrated sustained clinical efficacy of secukinumab in patients with moderate-to-severe hidradenitis suppurativa (HS) through 52 weeks."
    explanation: "Long-term extension data confirming sustained secukinumab efficacy through 104 weeks."
    evidence_source: HUMAN_CLINICAL
- name: NCT04179175
  phase: PHASE_III
  status: COMPLETED
  description: Extension trial for SUNSHINE/SUNRISE evaluating maintenance of HiSCR response with continuous versus interrupted secukinumab therapy through week 260.
  target_phenotypes:
  - preferred_term: Recurrent abscess formation
    term:
      id: HP:0002722
      label: Recurrent abscess formation
  evidence:
  - reference: clinicaltrials:NCT04179175
    supports: SUPPORT
    snippet: "The purpose of this extension study is to evaluate maintenance of Hidradenitis Suppurativa Clinical Response (HiSCR response) in either continuous or interrupted therapy (using a randomized withdrawal period) of two dose regimens and to assess long-term efficacy, safety and tolerability of Secukinumab in subjects with moderate to severe hidradenitis suppurativa"
    explanation: "Extension trial assessing long-term secukinumab maintenance therapy."
prevalence:
- population: Global
  percentage: 1.0
  notes: >
    Estimated prevalence varies widely by methodology and geography. Population-based
    studies report 0.1-1% globally, with screening questionnaire-based studies
    suggesting higher rates due to underdiagnosis. Diagnostic delay of 7-10 years
    contributes to underestimation of true prevalence.
  evidence:
  - reference: PMID:41784795
    reference_title: "Evaluating the diagnostic accuracy of a screening questionnaire for detecting hidradenitis suppurativa: a pooled analysis of accuracy measures from the Global Hidradenitis Suppurativa Atlas (GHiSA) study."
    supports: SUPPORT
    snippet: "Hidradenitis suppurativa (HS) is an inflammatory skin condition that is associated with a prolonged diagnostic delay of approximately 7-10 years."
    explanation: "The GHiSA global prevalence study documents the significant diagnostic delay contributing to underestimation of HS prevalence."
    evidence_source: HUMAN_CLINICAL
  - reference: PMID:41723775
    reference_title: "Economic Burden of Hidradenitis Suppurativa in Spain."
    supports: SUPPORT
    snippet: "Hidradenitis suppurativa (HS) is a highly disabling chronic inflammatory disorder affecting up to 1% of the Spanish population."
    explanation: "Spanish population data supports the upper bound of the 0.1-1% prevalence estimate."
    evidence_source: HUMAN_CLINICAL
- population: Spain
  percentage: 1.0
  notes: Up to 1% of the Spanish population; only approximately 10% of cases are diagnosed.
  evidence:
  - reference: PMID:41723775
    reference_title: "Economic Burden of Hidradenitis Suppurativa in Spain."
    supports: SUPPORT
    snippet: "Hidradenitis suppurativa (HS) is a highly disabling chronic inflammatory disorder affecting up to 1% of the Spanish population."
    explanation: "Direct prevalence estimate for Spain from economic burden analysis."
    evidence_source: HUMAN_CLINICAL
epidemiology:
- name: Comorbidity burden
  description: HS patients have significantly higher prevalence of multiple comorbidities compared to the general population, including tobacco use disorder, obesity, diabetes, chronic pain, and depression.
  factors:
  - tobacco use disorder
  - obesity
  - diabetes
  - chronic pain
  - depression
  evidence:
  - reference: PMID:41762022
    reference_title: "Burden of hidradenitis suppurativa in Germany: a retrospective claims data analysis and comparison with non-HS patients."
    supports: SUPPORT
    snippet: "Adult HS patients showed a significantly higher prevalence of comorbidities including a 3.58 (95% CI: 3.30; 3.85) higher prevalence for a mental/behavioral disorder due to tobacco, 2.72 (95% CI: 2.61; 2.83) for obesity, 2.56 (95% CI: 2.40; 2.73) for diabetes, 2.00 (95% CI: 1.86; 2.14) for pain and 1.69 (95% CI: 1.62; 1.76) for depression compared to matched non-HS individuals, respectively."
    explanation: "Large German claims data analysis quantifying significantly elevated comorbidity burden in HS patients."
    evidence_source: HUMAN_CLINICAL
- name: Disease progression from Hurley Stage I
  description: A substantial proportion of Hurley Stage I patients progress to more advanced stages over time. Smoking intensity, initial substage classification, and abscess count increase are independent predictors of progression.
  notes: Cumulative incidence of progression was 37.6% (49 to Hurley II, 1 to Hurley III) with an incidence density of 23 cases per 100 patient-years.
  factors:
  - higher number of cigarettes per day
  - Hurley Ic substage
  - increase in abscess count from baseline
  evidence:
  - reference: PMID:41678402
    reference_title: "Assessing disease progression in Hurley I hidradenitis suppurativa patients: a nested case-control study."
    supports: SUPPORT
    snippet: "cumulative incidence was 50 cases (37.6%) (49 to Hurley II; 1 to Hurley III) and incidence density was 23 cases/100 patients-year. After multivariate analysis, the following variables were significantly and independently associated to increasing Hurley stage: higher number of cigarettes/day (p = 0.009), Hurley Ic stage (p = 0.05) and the increase in abscess count from baseline (categorical) (p = 0.0003)."
    explanation: "Quantifies risk and predictors of disease progression from Hurley Stage I to more advanced stages."
    evidence_source: HUMAN_CLINICAL
- name: Diagnostic delay
  description: HS is associated with a prolonged diagnostic delay of approximately 7-10 years, attributed to low awareness among non-dermatologist healthcare professionals and clinical heterogeneity leading to misdiagnosis.
  minimum_value: 7
  maximum_value: 10
  unit: years
  evidence:
  - reference: PMID:41784795
    reference_title: "Evaluating the diagnostic accuracy of a screening questionnaire for detecting hidradenitis suppurativa: a pooled analysis of accuracy measures from the Global Hidradenitis Suppurativa Atlas (GHiSA) study."
    supports: SUPPORT
    snippet: "Hidradenitis suppurativa (HS) is an inflammatory skin condition that is associated with a prolonged diagnostic delay of approximately 7-10 years. The diagnostic delay can be attributed to various factors, including low awareness of diagnostic criteria among nondermatological healthcare professionals often leading to misdiagnosis."
    explanation: "Global multi-country study documenting the prolonged diagnostic delay in HS."
    evidence_source: HUMAN_CLINICAL
- name: Sex distribution
  description: HS disproportionately affects females, with female-to-male ratios reported between 2.4:1 and 3:1, though ratios vary by cohort and methodology.
  factors:
  - female sex predominance
  - hormonal influences
  evidence:
  - reference: PMID:33898701
    reference_title: "Characterizing perimenstrual flares of hidradenitis suppurativa."
    supports: SUPPORT
    snippet: "HS has been found to disproportionately affect women compared with men in a 2.4:1 ratio"
    explanation: "Population-based data documenting the female predominance in HS with a 2.4:1 female-to-male ratio."
    evidence_source: HUMAN_CLINICAL
  - reference: PMID:41678402
    reference_title: "Assessing disease progression in Hurley I hidradenitis suppurativa patients: a nested case-control study."
    supports: SUPPORT
    snippet: "Mean age was 37.54 (12.87) years, with a female-to-male ratio of 84:49."
    explanation: "Clinical cohort data confirming female predominance (approximately 1.7:1 in this Hurley I cohort, lower ratio possibly reflecting sex-specific referral patterns)."
    evidence_source: HUMAN_CLINICAL
- name: Hormonal influence
  description: HS typically presents after puberty and disproportionately affects females, suggesting a role for sex hormones. 62.4% of women report perimenstrual flares, predominantly in the premenstrual week, and spironolactone shows benefit in a subset of female patients.
  factors:
  - post-pubertal onset
  - perimenstrual flares
  - spironolactone responsiveness
  evidence:
  - reference: PMID:33898701
    reference_title: "Characterizing perimenstrual flares of hidradenitis suppurativa."
    supports: SUPPORT
    snippet: "The majority (176 of 282 women; 62.4%) reported HS worsening with menses, and 86.9% (153 of 176 women) noted that perimenstrual HS flares occurred always or often. Most women (138 of 175 women; 78.9%) reported that their HS flared in the week preceding menses."
    explanation: "Directly demonstrates hormonal influence on HS through quantification of perimenstrual flares occurring predominantly in the premenstrual period."
    evidence_source: HUMAN_CLINICAL
- name: Pediatric presentation
  description: HS can present in pediatric populations with distinct demographics and severe disease at diagnosis. Trisomy 21 is a notable comorbidity in pediatric HS with earlier onset.
  factors:
  - trisomy 21 comorbidity
  - earlier age of onset
  - severe disease at diagnosis
  evidence:
  - reference: PMID:41677500
    reference_title: "Clinical Characteristics and Management of Pediatric Hidradenitis Suppurativa: A Canadian Single-Centre Multidisciplinary Experience."
    supports: SUPPORT
    snippet: "Obesity (57.9%), acne (30.7%), folliculitis (23.1%), and trisomy 21 (23.1%) were the most common comorbidities. Patients with trisomy 21 had an age of HS onset 3 years younger (P = .0087)"
    explanation: "Pediatric HS data showing distinct comorbidity profile including high trisomy 21 association with earlier onset."
    evidence_source: HUMAN_CLINICAL
- name: Economic burden
  description: HS imposes substantial direct and indirect economic costs, with the largest components being informal care, treatment, and out-of-pocket expenses. Costs increase markedly with disease severity.
  notes: In Spain, mean annual cost per patient is approximately EUR 39,535 across all severities, with moderate and severe patients costing 64% and 171% more than mild patients respectively.
  evidence:
  - reference: PMID:41723775
    reference_title: "Economic Burden of Hidradenitis Suppurativa in Spain."
    supports: SUPPORT
    snippet: "The mean annual cost of treating all severities of patients with HS in Spain was €39,535.10. The largest cost components across all categories were informal care (46.05%), treatment (18.24%), out-of-pocket expenses (12.76%), loss of work productivity (10.82%), and surgery (5.62%)."
    explanation: "Comprehensive economic burden analysis quantifying direct and indirect costs of HS by severity level."
    evidence_source: HUMAN_CLINICAL
- name: Mortality risk
  description: HS patients aged 50 years and older have a numerically higher risk of death compared to matched non-HS individuals, with substantial years of life lost.
  evidence:
  - reference: PMID:41762022
    reference_title: "Burden of hidradenitis suppurativa in Germany: a retrospective claims data analysis and comparison with non-HS patients."
    supports: SUPPORT
    snippet: "HS patients aged ≥ 50 years had a numerically higher risk of death (risk ratio 1.57; 95% CI 0.96-2.17). Among deceased HS patients, the mean number of years of life lost ranged from 20.46 to 25.91 during the period 2020-2022."
    explanation: "Claims data analysis revealing increased mortality risk and substantial years of life lost in HS patients."
    evidence_source: HUMAN_CLINICAL
- name: Squamous cell carcinoma risk
  description: HS is associated with an increased risk of cutaneous squamous cell carcinoma (SCC), particularly in chronically affected perianal and gluteal regions with long-standing disease.
  factors:
  - chronic inflammation
  - long disease duration
  - perianal and gluteal involvement
  evidence:
  - reference: PMID:37545826
    reference_title: "Hidradenitis suppurativa and squamous cell carcinoma: a systematic review of the literature."
    supports: SUPPORT
    snippet: "Hidradenitis suppurativa (HS) is a chronic disease which is often recurrent and occurs as abscesses of the apocrine gland. The most common locations of HS are gluteal/perianal, axillary or inguinal. It is reasonable to assume that squamous cell carcinoma may arise from HS."
    explanation: "Systematic review establishing the association between chronic HS and SCC development, particularly in gluteal/perianal locations."
    evidence_source: HUMAN_CLINICAL
datasets:
- accession: geo:GSE294009
  title: Spatial Transcriptomic Analysis of Early and Late Stages of Hidradenitis Suppurativa
  description: >-
    Spatial transcriptomics of early and late HS skin lesions characterizing
    inflammatory nodules, abscess formation, and sinus tract development at
    spatial resolution.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  data_type: SPATIAL_TRANSCRIPTOMICS
  sample_count: 204
  conditions:
  - early-stage HS lesions
  - late-stage HS lesions
  notes: Large spatial transcriptomics dataset (204 samples) comparing early and late HS stages.
- accession: geo:GSE306437
  title: Unique B and plasma cell signature differentiates hidradenitis suppurativa from psoriasis and atopic dermatitis
  description: >-
    RNA-seq comparing HS, psoriasis, and atopic dermatitis to identify
    disease-specific immune signatures. Reveals unique B cell and plasma cell
    enrichment in HS versus other inflammatory skin diseases.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  data_type: BULK_RNA_SEQ
  sample_count: 118
  conditions:
  - hidradenitis suppurativa
  - psoriasis
  - atopic dermatitis
  - healthy controls
  findings:
  - statement: Unique B and plasma cell transcriptomic signature distinguishes HS from psoriasis and atopic dermatitis.
- accession: geo:GSE315442
  title: Transcriptomic profiling reveals distinct molecular signatures among lesion types in hidradenitis suppurativa
  description: >-
    Bulk RNA sequencing comparing distinct HS lesion types to identify
    lesion-specific molecular signatures.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  data_type: BULK_RNA_SEQ
  sample_count: 48
  conditions:
  - HS lesional skin (multiple lesion types)
  - non-lesional HS skin
- accession: geo:GSE295706
  title: "Early versus late hidradenitis suppurativa: Type 17 T-cell and B-cell inflammation precedes dermal tunnel and tertiary lymphoid structure formation"
  description: >-
    RNA-seq of early versus late HS demonstrating that Th17 and B-cell
    inflammation precedes the formation of dermal tunnels and TLS.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  data_type: BULK_RNA_SEQ
  sample_count: 6
  conditions:
  - early-stage HS
  - late-stage HS
  findings:
  - statement: Type 17 T-cell and B-cell inflammation precedes tunnel and TLS formation.
classifications:
  harrisons_chapter:
  - classification_value: skin disorder