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Condition created 2026-08-24 · updated 2026-08-24
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Hidradenitis Suppurativa

Second of two entities in Part II, Chapter 16 (split from Pilonidal Disease as a genuinely distinct clinical entity, per this wiki's established split rule). Hidradenitis suppurativa (HS), or acne inversa, is a chronic, relapsing, inflammatory skin disease of the apocrine gland-bearing skin folds (axilla, inguinal, inframammary, perineal/perianal regions) that typically begins after puberty. Presents with painful subcutaneous nodules that can spontaneously rupture/coalesce into deep dermal, exquisitely painful abscesses; ultimately heals with fibrosis, dermal contractures, induration, and chronic sinuses. Most commonly affected region is the axilla (70%), followed by perineum/groin. Associated with marked quality-of-life reduction and high comorbid-mental-illness incidence.

Epidemiology and pathogenesis

US population prevalence estimated at 0.1% (98 per 100,000). Women affected >2x as often as men; prevalence highest at age 30–39. Prevalence among African American patients >3x that of white patients. Only 2% of cases occur before age 11; 7.7% report onset before age 13 (early onset associated with stronger genetic susceptibility and more widespread disease).

Once believed to result from apocrine gland infection, HS is now considered a disease of follicular occlusion: follicular occlusion → follicular rupture → discharge of keratin/bacteria into the surrounding dermis → foreign-body-type immune response, with increasing evidence for a role of Th17 cells and enhanced IL-17/IL-1β expression (implicating an auto-inflammatory pathogenesis). Bacteria and biofilms are likely contributory but secondary drivers of inflammation.

Modifiable risk factors: smoking (adjusted OR 1.9 for developing HS among smokers vs. nonsmokers in a US cohort; meta-analysis OR 4.26 for current-smoker association) and obesity (OR 1.12 per one-unit BMI increase). Mechanical stress worsens HS via increased follicular occlusion/rupture. Factors implicated in development: host defenses, genetics, endocrine abnormalities, obesity, smoking, environmental factors.

Clinical presentation and diagnosis

Diagnostic delay is a significant problem — average delay to first physician visit 2.3±5.0 years, overall diagnostic delay 7.2±8.7 years. Presentation ranges from a single open comedone to multiple painful, swollen nodules, generally with little purulent discharge; the inflammatory process often waxes and wanes over weeks to years. Chronic changes (sinus tract formation, contractures, fibrosis) develop with disease progression. Substantial productivity impact: in one 100-patient study, 21% reported missing work, 60% reported activity-impairing loss of productivity in the preceding week; 72% reported daily activity impairment, with impairment correlating with Hurley stage III disease (see below).

Diagnosis is made by lesion morphology (nodules, abscesses, tunnels, scars), location (axillae, inframammary folds, groin, perigenital, perineal), and lesion progression (two recurrences within 6 months, or chronic/persistent lesions ≥3 months). Differential in the perineal/genital area is primarily HS vs. other subcutaneous tunneling disease; biopsy if uncertain. Key differentiators: absence of midline pits distinguishes HS from Pilonidal Disease; absence of anal canal involvement distinguishes HS from Crohn's disease and benign anal fistula.

Disease severity classification

  • Hurley classification: Stage I — transient nonscarring inflammatory lesions; Stage II — separate recurrent lesions with tunnel formation/scarring, single or multiple lesions separated by normal-looking skin; Stage III — coalescent lesions with tunnel formation, scarring, and inflammation across the region. Criticized because many patients have multifocal disease across regions rather than uniform severity in one area; a revised system subdivides Stages I–II into mild (A), moderate (B), and severe (C) substages based on extent/inflammation (Stage III is not subcategorized — it is not always severe). Also criticized as a static score not responsive to inflammatory-component change.
  • Sartorius score — counts/classifies/weights involved predetermined anatomical regions, adds points for longest inter-lesion distance within an affected region and for Hurley III involvement, summed to an overall severity score.
  • Hidradenitis Suppurativa Clinical Response (HiSCR) — developed/validated as the primary RCT endpoint for adalimumab studies; objective counting of HS lesions, correlates significantly with Hurley stage, Sartorius score, HS Physicians Global Assessment, and patient-reported pain/quality- of-life/work-productivity measures.

In a review of 826 HS patients: 45% Hurley I, 41% Hurley II, 13% Hurley III. Severity associated with male sex, disease duration, BMI, smoking pack-years, and axillary/perianal/mammary lesion location. Women had earlier onset and more inguinal/mammary lesions with more frequent HS family history; men more commonly had gluteal/perianal/atypical lesions and a history of severe acne.

Comorbidities: metabolic disorders (obesity, metabolic syndrome) are the most commonly associated conditions. Also associated with inflammatory bowel disease, autoinflammatory disease, spondyloarthritis, some genetic keratin disorders, and increased skin-tumor risk — possibly reflecting shared genetic/environmental factors or inflammatory pathways. Well-established link between acne and both HS and pilonidal disease.

Treatment

Multidisciplinary: medical therapies (topical/systemic antibiotics, hormonal agents, biologics) through surgery (incision and drainage to wide local excision with skin grafting). Surgery is typically reserved for intractability and acute abscess formation, but is one of the most successful treatments available. Individualized, chronic-relapsing-disease treatment planning with clear patient education and elicited goals is essential before choosing a treatment path.

Topical therapy

Clindamycin lotion (1%) is the only topical antibiotic studied — a placebo-controlled RCT (30 patients) found significantly better effect than placebo on abscesses/nodules/pustules over 3 months; primarily used for Hurley stage I or mild stage II, dosed twice daily for 3 months. Resorcinol (a keratolytic/anti-inflammatory phenol derivative) showed significant lesion-size and pain-score reduction by days 7 and 30 in a 32-patient study.

Systemic antibiotics

Commonly used for HS flares from secondary bacterial infection; tetracycline and rifampicin may also have immunomodulatory properties (tetracycline suppresses neutrophil migration/chemotaxis, inhibits matrix metalloproteinase). Tetracycline 500mg BID vs. topical clindamycin showed no significant difference in an RCT of 46 Hurley I/II patients — tetracycline can be first-line for widespread Hurley I/mild II for up to 4 months. Clindamycin 300mg BID + rifampicin 600mg daily (or 300mg BID) combination therapy: a 116-patient study found significantly decreased Sartorius scores and improved quality of life; another prospective study (26 patients, 12 weeks + 1-year follow-up) found 73% initial clinical response, 41% sustained at 1 year (mean relapse at 4.2 months post-cessation). Can be used first-line for moderate/severe HS for up to 10 weeks.

Biologics

Adalimumab (40mg SC weekly) — RCT of 154 moderate-to-severe HS patients who had failed antibiotic therapy showed significant HiSCR/pain-score improvement and increased quality of life/work productivity, reproduced in 3 additional RCTs. Recommended as first-line biologic for patients unresponsive/intolerant to oral antibiotics. Infliximab (5mg/kg) — RCT/crossover trial found no significant HiSCR difference vs. placebo, though more IFX patients achieved a 50% lesion-count reduction, with significant quality-of-life/pain improvement; recommended as a second-line option after adalimumab failure. Anakinra (IL-1 receptor antagonist) and ustekinumab (human IgG1κ anti-IL-12/23 monoclonal antibody) have shown efficacy as alternate therapies in recent studies.

Biologics as a surgical adjunct: some evidence supports biologics combined with surgery to decrease recurrence vs. surgery alone. In one study (68 patients, mean 10-year disease duration, 63% Hurley III), biologic-treated patients had a larger drop in Sartorius score/active nodule count than those never on biologics; effect was greater with concurrent surgery; timing of biologics relative to surgery did not affect efficacy. Patients on biologics were most likely to achieve a 75% reduction in active nodule count. In another study (11 combined surgical+biologic patients vs. 10 radical-resection -alone patients; infliximab n=8, ustekinumab n=3, continued ~10.5 months post-closure): recurrence 19% (combined) vs. 38% (surgery-alone) of previously treated sites (p<0.01); disease-free interval ~1 year longer on average with combined therapy (p<0.001); new disease developed in 18% (combined) vs. 50% (surgery-alone) (p<0.001). No adverse events noted among biologic-treated patients.

Other medical therapies

Androgens influence HS (pregnancy/menstrual-cycle symptom effects in many patients), but hormonal- therapy evidence is limited — the only RCT (24 women, double-blind crossover) compared ethinyl estradiol/norgestrel vs. ethinyl estradiol + cyproterone acetate, both with similar improvement (12/24 improved or cleared completely). Metformin — reduces hepatic gluconeogenesis, improves insulin-mediated glucose uptake, reduces ovarian androgen production, has anti-inflammatory properties; a 24-week trial (mostly women with PCOS features) showed clinical/quality-of-life improvement. Retinoids — historically used (HS once thought similar to acne vulgaris), but results disappointing given current follicular-occlusion pathogenesis understanding: across 7 uncontrolled cohort/case studies (207 patients on isotretinoin monotherapy), only 41% (85/207) improved, with better response in milder disease — most useful in patients with concomitant nodulocystic acne.

Laser therapies

Reduce HS flare occurrence by decreasing hair follicles/sebaceous glands/bacteria in affected areas; best results with individualized, disease-severity-based selection. Nd:YAG laser — RCT (22 patients, half-body treated vs. control) using a modified Sartorius scoring system found 65% overall HS-severity reduction by 3 months (73% inguinal, 62% axillary, 53% inframammary sites) — statistically significant vs. control. CO2 laser excision — may help more extensive disease, high patient satisfaction, but studied only in Hurley stage II with higher recurrence than wide excision; a 24-patient study (27-month mean follow-up) found 22/24 resolution with no HS recurrence, healing over a median of 4 weeks (vaporization usually reaching deep subcutaneous fat/fascia).

Surgery

Reserved for medical-therapy failure with debility/pain from lesions, but can achieve excellent outcomes. Goal: excise the entire pilosebaceous/hair-bearing region involved (axilla, inframammary fold, groin, perineum) down through subcutaneous fat and even fascia as appropriate to eliminate the pilosebaceous unit. Extent depends on disease extent and patient goals, ranging from simple I&D to wide local excision with skin grafting. For tense/painful abscesses, surgical drainage is required (no medical therapy alone) — understood as a temporizing measure, with disease recurrence inevitable.

  • Deroofing — the roof of a lesion is surgically removed, floor left exposed, to avoid the morbidity of a large wound. A 44-patient study (73 deroofing procedures, recurrent Hurley I/II lesions) showed 83% no recurrence at median 34-month follow-up; the other 17% recurred at median 4.6 months. 90% of respondents would recommend the procedure to others.
  • STEEP procedure (skin tissue-sparing excision with electrosurgical peeling) — a variation using an electrosurgical loop to excise overlying skin, reducing collateral injury to surrounding normal tissue/subcutaneous fat via successive tangential excisions down to the epithelialized sinus-tract floor; healing by secondary intention. 4% recurrence rate — this tissue-sparing technique shows low recurrence, high satisfaction, relatively short healing times, and favorable cosmetic outcomes without contractures.
  • Wide local excision — mainstay of traditional surgery for more extensive disease; can achieve a disease-free state at the excision site. Small wounds can be closed primarily; larger wounds may be left to heal by secondary intention, closed with skin grafts, or (rarely) require colostomy diversion for perineal/perianal wounds. Because surgery alone does not alter disease biology elsewhere, the trade-off between excision extent, surgical morbidity, and reducing future-lesion risk is an important consideration.

Comparative surgical outcomes: in a 590-patient series (excision, deroofing, or drainage), drainage had the highest recurrence, deroofing and wide excision were about equal in effectiveness; most patients were white (91%), men (57%), smokers (58%), Hurley III (81%). Postop complications occurred in 2.5%, postop recurrence in 24% (necessitating reoperation in 12% of those). Recurrence risk increased with younger age (HR 0.8), multiple surgical sites (HR 1.6), and drainage-type procedures (HR 3.5); operative location, disease severity, gender, and operative extent did not influence recurrence rate. In a 79-patient/220-operative-site retrospective review over 4 years: 25% recurrence, median disease-free interval 8 months, two-thirds of recurrences (63%) needing repeat excisional surgery; recurrence differed significantly by body location (axilla lowest recurrence, groin highest; no significant difference in wound-complication rates by location); smoking, BMI, Hurley grade, closure method, and excision size did not affect local cure rate. A meta-analysis of 22 articles found average recurrence: wide excision 13.0%, local incision 22.0%, deroofing 27.0%. Within wide excision, recurrence by closure method: primary closure 15%, flaps 8%, grafting 6%.

Patient-reported outcomes: median satisfaction score 17/20 (function, aesthetics, satisfaction after all interventions), though scores lower after fasciocutaneous flaps than primary closure, secondary- intention healing, or split-thickness skin grafting. In a survey of 111 Hurley III patients following excision/unroofing: 85% satisfied/very satisfied, 96% glad they underwent surgery, 83% would recommend surgery to a friend/relative; 62% satisfied/very satisfied with healed-wound appearance. Retrospective mean quality-of-life score increased from 5 preoperatively to 8.4 postoperatively (p<0.001).

Negative pressure wound therapy has been shown to shorten the duration between excision and delayed closure/grafting — theorized to improve wound healing via increased blood flow/granulation tissue formation and reduced bacterial load. Comparisons among NPWT-alone vs. silver dressings vs. dermal regeneration templates (e.g. Integra) remain limited.

Conclusion

HS is a chronic disease that can cause significant debility/suffering, most commonly presenting in patients' prime working years with a substantial productivity/quality-of-life burden from its waxing and waning course. Treatment should be multidisciplinary with a focus on managing patient goals and expectations. Topical/oral antibiotic therapy can be effective for smaller/milder disease; biologic agents have shown efficacy for more widespread/severe disease with evolving inflammatory-target understanding; surgery remains important, spanning I&D through wide local excision with skin grafting or healing by secondary intention.

  • Pilonidal Disease — the first entity covered in this same source chapter; distinguished on exam by absence of midline pits.
  • Anal Stenosis — already listed "suppurative processes (complex abscess/fistula, hidradenitis)" in its differential; this page and Pilonidal Disease provide the fuller content that mention was gesturing at.
  • Pruritus Ani — HS is listed among the dermatologic-disorder causes of anal pruritus in that page's differential; that chapter also notes HS has three progressive stages (abscess-only through widely-separated recurrent lesions to a fully interconnected-tract stage), consistent with this page's Hurley classification.

Open items / gaps

  • Absence of anal canal involvement is noted as a key HS-vs-Crohn's/anal-fistula differentiator, but this page has not yet been cross-linked against Crohn Disease or Anal Fistula pending those pages' own review for HS mentions — worth a follow-up pass if either page is revisited.
  • No primary-literature source yet for the cited RCT/cohort data (adalimumab, infliximab, clindamycin/rifampicin, Nd:YAG laser trials) — known only via this textbook chapter's synthesis.