Authors: Vanessa Ngan, Staff Writer, Dr Amanda Oakley, Dermatologist, New Zealand, 1997. Updated December 2015. Revised by: Dr Abdulhadi Jfri, PGY-5 Dermatology Resident, McGill University, Montreal, Canada. Dr Elizabeth O’Brien, Assistant Professor of Dermatology, McGill University, Montreal, Canada, January 2021. Minor amendment by Ian Coulson, Dermatologist, Feb 2025
Hidradenitis suppurativa (HS), also called acne inversa, is a chronicinflammatory skin condition that affects apocrinegland-bearing skin in the axillae, groin, and under the breasts. It is characterised by persistent or recurrent boil-like nodules and abscesses that culminate in a purulentdischarge, sinuses, and scarring.
HS can have a significant psychological impact, and many patients suffer from anxiety, depression, and impairment of body image.
Who gets hidradenitis suppurativa?
Hidradenitis suppurativa often starts at puberty, is most active between the ages of 20 and 40 years, and in women can resolve at menopause. It is three times more common in females than in males. Associations and risk factors include:
Family history of HS; 30–40% report at least one other family member affected
Hidradenitis developing at a young age in childhood or early adolescence may be an indicator of underlying precocious puberty.
What causes hidradenitis suppurativa?
Although ‘hidradenitis’ implies an inflammatory disease of the sweat glands, we now know that HS is an autoinflammatory syndrome. The exact pathogenesis is not yet understood. Factors involved in the development of acne inversa include:
Inflammation causing rupture of the follicular wall, destroying sebaceous and apocrine glands and ducts.
What are the clinical features of hidradenitis suppurativa?
Acne inversa can affect single or multiple areas in the axillae, neck, inframammary fold, and inner upper thighs. Anogenital involvement most commonly affects the groin, mons pubis, vulva, scrotum, perineum, buttocks, and perianal folds.
HS is characterised clinically by:
Open double-headed comedones
Painful firm papules and nodules
Pustules, fluctuantpseudocysts, and abscesses
Draining sinuses linking inflammatory lesions
Hypertrophic and atrophic scars.
Clinical phenotypes of hidradenitis suppurativa (HS)
How is the severity of hidradenitis suppurativa assessed?
Disease severity and extent is measured by clinical and ultrasound assessment at the time of diagnosis and when monitoring response to treatment. There are a number of severity scales for HS [see guidelines for Hidradenitis suppurativa: severity assessment].
The Hurley system, the most widely used assessment tool, describes three clinical stages.
Stage I: solitary or multiple isolated abscess formation without sinus tracts or scarring.
Stage II: Recurrent abscesses, single or multiple widely spaced lesions, with sinus tract formation.
Stage III: Diffuse involvement of an area with multiple interconnected sinus tracts and abscesses.
What are the complications of hidradenitis suppurativa?
Complications of HS can include:
Secondary infection
Psychological effects and negative impact on quality-of-life
Small increased incidence of abdominal aorticaneurysm.
How is hidradenitis suppurativa diagnosed?
The diagnosis of acne inversa requires all three components of the triad to be met:
Characteristic lesions
Typical distribution
Presence and recurrence of lesions.
Swabs for bacteriology are typically negative, which is a clue to diagnosis. Extensive investigations are rarely required. Investigations may be indicated to exclude a differential diagnosis, for possible complications, to identify comorbidities, or for planned treatment.
What is the differential diagnosis for hidradenitis suppurativa?
Differential diagnoses for hidradenitis suppurativa can include the following conditions.
Short oral course for acute staphylococcal abscess
Tetracyclines as a single agent
Prolonged courses of at least three months of combination antibiotics: clindamycin plus rifampicin; tetracyclines plus rifampicin; fluoroquinolone plus metronidazole plus rifampicin
Intravenous ertapenem - it is possible to home administer via an indwelling catheter for 12 weeks with improvement in both pain and HS severity index.
Biologics: adalimumab is the only biologic approved in Australia and New Zealand for treating hidradenitis suppurativa [see Tumour necrosis factor inhibitors]
Others are under investigation in clinical trials
Adalimumab and other biologics have been reported to paradoxically trigger acne inversa
In several European countries, sekukinumab has received licencing
Other systemic medical treatments used off-label: metformin, acitretin, dapsone, colchicine, and zinc gluconate.
Surgical and other procedural measures
Incision and drainage of acute abscesses
Local excision of persistent nodules, abscesses, and sinuses
Deroofing and curettage of persistent abscesses and sinuses
Radical excisional surgery of an entire affected area
Laserablation (CO2) of nodules, abscesses, and sinuses
Laser/light hair removal.
What is the outcome for hidradenitis suppurativa?
Hidradenitis suppurativa tends to improve in pregnancy in those who usually have flares during menstruation. Normal vaginal delivery is possible unless the patient has extensive painful genital lesions.
HS is a chronic scarring condition. Spontaneous remission may occur with time, but scarring persists.
Early diagnosis and treatment are required to minimise lasting damage.
Bibliography
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Wendland, Z., Rypka, K., Herzog, C., Greenlund, L., Fulk, T., Gravely, A., Westanmo, A., Garg, A., & Goldfarb, N. (2025). Prevalence of abdominal aortic aneurysm in patients with hidradenitis suppurativa in the Veterans Affairs Health Care System. British Journal of Dermatology, 192(1), 160–162. doi:10.1093/bjd/ljae325. Journal
Global HS COVID-19 Registry — Health professionals complete de-identified case histories of patients with hidradenitis suppurativa with confirmed or suspected COVID-19