Hidradenitis suppurativa (acne inversa)
Definition & Pathogenesis
- Acne inversa / Hidradenitis suppurativa (HS) = chronic-recurrent inflammatory skin disease of the pilosebaceous unit in areas with apocrine sweat glands (axillary, inguinal, anogenital, submammary).
- Pathomechanism: Pathogenetically central is follicular occlusion with rupture into the dermis and neutrophil-rich inflammation → sinus tract formation + scarring.
- Key cytokines + cells: Driving factors are TNF-α + IL-1β + IL-17 plus neutrophils + macrophages.
- Risk factors: Classic factors are smoking + obesity + γ-secretase mutations.
- Comorbidities: Acne conglobata, Crohn's disease, Spondyloarthritis, PCOS, Pyoderma gangraenosum, metabolic syndrome, depression.
Clinical Presentation & Severity
- Clinical presentation: painful, deep-seated inflammatory nodules + abscesses + sinus tracts + hypertrophic scars + double comedones in typical locations.
- Hurley Stages (clinical-historical):
- Stage I: isolated nodules/abscesses
- Stage II: recurrent abscesses + scattered sinus tracts / scars
- Stage III: diffusely affected + communicating sinus tract systems
- iHS4-Score (modern, for monitoring disease course): Scoring system based on nodules + abscesses + sinus tracts — ≤ 3 mild, 4–10 moderate, > 10 severe.
Acne Tetrad (classic)
The classic acne tetrad includes acne conglobata + AI + pilonidal sinus.
Diagnostics
- Clinical history and examination: typical localization + ≥ 2 flares in 6 months.
- Ultrasound (≥ 7.5 MHz): subclinical sinus tracts, drainage pathways.
- MRI for perianal / anorectal involvement (Crohn's disease DD).
- Laboratory tests: ESR / CRP, CBC, HbA1c, lipid profile (comorbidities), no specific marker.
Differential diagnoses
- Abscess
- Carbuncle
- Eccrine hidrocystoma
- Candida intertrigo
- Acne vulgaris
- Psoriasis inversa
- Scrofuloderma / Tuberculosis cutis colliquativa
- PAPASH syndrome
Practise Hidradenitis suppurativa (acne inversa) in the app
Flashcards with spaced repetition, exam questions and spot-the-diagnosis on this topic – in DermaFuchs, free of charge.
In the DermaFuchs app: 9 flashcards · 5 clinical images
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More diseases of the skin appendages
- Acne fulminans
- Acne vulgaris
- Alopecia areata
- Androgenetic alopecia
- Folliculitis (infectious)
- Lichen planopilaris
- Milia (milium)
- Perioral dermatitis
Note: This page is intended for medical education and does not replace diagnosis or treatment decisions in individual cases. Treatment and follow-up content is available in the app.