12-phase flow (12)

1. 1FRAME
   Frame HS as a CHRONIC recurrent inflammatory follicular-occlusion disease of apocrine-bearing intertriginous skin and a SYSTEMIC inflammatory condition with a major comorbidity burden — NOT a simple recurrent skin infection treatable by drainage alone. Severity is the static Hurley stage + the dynamic IHS4 inflammatory load. The not-to-miss is SCC arising in long-standing perianal/buttock HS.
   advance: chronic systemic HS framing set; acute-flare + SCC + mental-health escape routes noted
2. 2ENTRY
   Recognise recurrent painful intertriginous nodules/abscesses with sinus tracts/scarring vs the acute-severe-abscess / comorbidity-cluster entries; capture lesion sites up front (apocrine-bearing distribution is a core diagnostic element).
   inputs: lesion_sites_and_distribution
   actions: workup.chronic_pruritus
   advance: entry trigger present; lesion distribution recorded
3. 3CONTEXT
   Build the diagnostic + comorbidity context: HS morphology (nodules/abscesses/sinus tracts/bridged scars/double comedones), recurrence/chronicity in typical sites, and the systemic-inflammatory comorbidity cluster — smoking, BMI/metabolic syndrome, IBD, spondyloarthropathy, PCOS, depression. Post-pubertal onset; pre-pubertal onset → endocrine eval. The diagnostic triad (typical lesions + typical sites + recurrence) is clinical — no test confirms HS.
   inputs: lesion_morphology_nodule_abscess_sinus_comedone, recurrence_chronicity, smoking_status, bmi_weight, hs_comorbidities_metabolic_ibd_spa_pcos_mental, age_and_pubertal_status
   actions: workup.chronic_pruritus
   advance: clinical triad supported; full comorbidity cluster screened
4. 4RED_FLAGS
   Acute severe abscess / secondary cellulitis with systemic toxicity → acute flare path (I&D + flare antibiotic; route infection if septic). Depression/suicidality screen-positive → urgent mental-health routing (suicidality is over-represented in HS). These are recognised here and escalated/routed.
   inputs: secondary_infection_or_systemic_sepsis_signs, depression_suicidality_screen
   actions: panel.cbc, panel.inflammation
   advance: acute infection + mental-health red flags screened and escalated/routed if present
5. 5INITIAL_WORKUP
   HS is a clinical diagnosis — no confirmatory test. Targeted workup is for (a) biologic/antibiotic readiness (CBC, CRP, LFT, latent-TB + hepatitis before any biologic) and (b) the differential/comorbidity (lesion swab only if secondary infection suspected — HS lesions are frequently culture-negative or commensal; metabolic screen; biopsy of a non-healing lesion for SCC). Imaging (ultrasound/MRI) maps occult sinus tracts for surgical planning.
   inputs: cbc_with_differential, inflammatory_markers_crp, latent_tb_and_infection_screen, lft
   actions: panel.cbc, panel.inflammation, panel.lft, panel.renal
   advance: pre-biologic safety + metabolic + SCC-biopsy decisions actioned as indicated
6. 6BRANCHING_WORKUP
   Follicular-occlusion / recurrent-abscess decision tree: typical sites + sinus tracts + double comedones + recurrence → HS; recurrent S. aureus abscess WITHOUT tracts/comedones, atypical sites, culture-positive → recurrent furunculosis (route derm.skin-abscess.core.v1); perianal disease with GI symptoms / metastatic cutaneous Crohn → GI/IBD route; severe nodulocystic acne + pilonidal + dissecting scalp cellulitis → follicular-occlusion tetrad (acne conglobata — derm.acne-vulgaris.core.v1, narrate until authored); pilonidal sinus (natal cleft only); LGV/STI abscess (inguinal, sexual history); epidermoid cyst (single, punctum); cutaneous TB / actinomycosis (sinus + organisms). Long-standing perianal/buttock HS with a non-healing indurated lesion → biopsy for SCC before any escalation.
   inputs: non_healing_indurated_lesion_long_standing
   actions: workup.chronic_pruritus
   advance: HS confirmed clinically OR an alternative diagnosis assigned + routed; SCC excluded/biopsied in long-standing perianal/buttock disease
7. 7DIFFERENTIAL
   Terminal follicular-occlusion / recurrent-abscess differential with named pivots: HS vs recurrent S. aureus furunculosis (pivot: recurrence in apocrine sites + sinus tracts + double comedones; route derm.skin-abscess.core.v1) vs metastatic/cutaneous Crohn (perianal knife-cut fissures + GI symptoms — GI route) vs acne conglobata / follicular-occlusion tetrad (nodulocystic acne + pilonidal + dissecting cellulitis pivot) vs pilonidal disease (natal-cleft-only pivot) vs LGV/STI abscess (inguinal + sexual exposure + serology pivot) vs epidermoid cyst (solitary + central punctum pivot) vs cutaneous TB / actinomycosis (chronic sinus + organism/culture pivot) vs SCC arising in chronic HS (non-healing indurated long-standing perianal/buttock — biopsy pivot).
   advance: single best diagnosis selected; SCC actively excluded in long-standing disease; overlapping follicular-occlusion phenotypes flagged
8. 8RISK_STRATIFICATION
   Severity is dual: static HURLEY stage (I/II/III — extent of irreversible tract/scar tissue, drives the surgical decision for the predominantly non-inflammatory form) PLUS the dynamic IHS4 (nodes ×1 + abscesses ×2 + draining tunnels ×4 → mild ≤3 / moderate 4–10 / severe ≥11 — drives the medical ladder for the inflammatory form). Mild → topical ± foundational non-pharm; moderate → systemic antibiotic ± hormonal; moderate–severe/refractory → biologic; extensive Hurley III tract burden → surgery + biologic. Captured narratively (Hurley/IHS4 are schema-blocked as TS calculators).
   inputs: hurley_stage, ihs4_inflammatory_load
   advance: Hurley stage + IHS4 tier assigned; medical-vs-surgical pathway decided
9. 9TREATMENT
   FOUNDATIONAL non-pharm always (smoking cessation, weight optimisation, friction reduction, pain management, wound care) + the severity-driven ladder. Step 1 mild (Hurley I / low IHS4): topical clindamycin, antiseptic washes (chlorhexidine / benzoyl peroxide), resorcinol peel. Step 2 moderate: systemic antibiotic anti-inflammatory courses — doxycycline/tetracycline, or clindamycin+rifampicin; hormonal (spironolactone / COC / metformin, especially with PCOS/metabolic). Step 3 moderate–severe/refractory: biologics — adalimumab (1st FDA-approved, PIONEER), secukinumab (IL-17A, SUNSHINE/SUNRISE), bimekizumab (IL-17A/F, BE HEARD); intralesional triamcinolone for the acute inflamed nodule. Step 4 surgical: I&D (acute abscess — symptomatic only, high recurrence), deroofing, local/wide excision of chronic sinus-tract regions, CO2 laser; continue the biologic perioperatively. Medical+surgical combination is the holistic standard. Acute flare path: painful abscess → I&D + intralesional steroid + flare antibiotic — do NOT rely on I&D alone for cure. Gate on pregnancy/age/comorbidity/latent-TB.
   inputs: pregnancy_lactation, age_and_pubertal_status, creatinine_potassium
   advance: foundational non-pharm + appropriate ladder step started; biologic safety-screened; surgical regions defined where Hurley dictates
10. 10DISPOSITION
    Predominantly outpatient/derm-clinic + multidisciplinary (derm, plastic/colorectal surgery, mental health, endocrine/bariatric). Inpatient/operating theatre only for extensive Hurley III surgery, severe disabling flare needing inpatient analgesia/IV therapy, or secondary sepsis. Mental-health and SCC routed OUT by service.
    inputs: secondary_infection_or_systemic_sepsis_signs
    advance: disposition documented; inpatient only for extensive surgery / severe flare / sepsis; multidisciplinary follow-up arranged
11. 11MONITORING
    Disease: IHS4 + Hurley re-stage + pain + DLQI at the agent-appropriate interval (biologic effect judged by ~12–16 wk HiSCR50; antibiotic courses reassessed at 8–12 wk). Drug safety: biologic latent-TB/infection vigilance + injection-site; clindamycin+rifampicin tolerability (GI, hepatic, drug interactions) and duration; tetracycline photosensitivity/GI; spironolactone potassium/BP; antibiotic-stewardship (anti-inflammatory courses are time-limited, not indefinite). Re-screen depression and metabolic comorbidities.
    inputs: inflammatory_markers_crp, creatinine_potassium
    actions: panel.cbc, panel.lft
    advance: IHS4/Hurley response assessed at the agent interval; drug-class safety + comorbidity surveillance on schedule
12. 12FOLLOWUP
    Chronic-disease maintenance: lifelong smoking-cessation + weight-management reinforcement, friction/wound-care self-management, written flare action plan, biologic maintenance with continued TB/infection vigilance, periodic comorbidity surveillance (metabolic syndrome, IBD, spondyloarthropathy, PCOS, depression/suicidality), antibiotic-stewardship review, and SCC surveillance of long-standing chronic perianal/buttock sites. Multidisciplinary continuity; reconsider surgery for residual tract burden once inflammation controlled.
    inputs: smoking_status, hs_comorbidities_metabolic_ibd_spa_pcos_mental
    actions: workup.chronic_pruritus
    advance: action plan + lifestyle reinforcement + comorbidity & SCC surveillance + stewardship review documented