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Hidradenitis suppurativa

What is hidradenitis suppurativa?

Hidradenitis suppurativa is an inflammatory skin disease that is characterised by recurrent boil-like lumps (nodules and abscesses) that culminate in pus-like discharge, difficult-to-heal open wounds (sinueses) and scarring. It commonly occurs on apocrine sweat gland-bearing skin such as in the groin, the underarms (axillae) and under the breasts.

The term "hidradenitis" implies it starts as an inflammatory disorder of sweat glands, which is now known to be incorrect. Hidradenitis suppurativa is also known as ‘acne inversa’ (inverse acne).

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Hidradenitis suppurativa Hidradenitis suppurativa Hidradenitis suppurativa
Hidradenitis suppurativa

What causes hidradenitis suppurativa and who gets it?

The exact cause of hidradenitis suppurativa remains unclear. The condition is a disorder of follicular occlusion. This begins with follicular plugging that obstructs the apocrine gland ducts and leads to perifolliculitis (inflammation around the ducts). This is followed by rupture of the follicular epithelium, bacterial infection and formation of sinus tracts between abscesses under the skin, ie the characteristic symptoms and signs of hidradenitis suppurativa.

The following are thought to play a role in the development of hidradenitis suppurativa.

Women are affected by hidradenitis suppurativa three times as often as men; the reason for this is unknown. The condition most commonly occurs between 20–40 years and coincides with the post-pubertal increase in androgen levels. Disease onset rarely occurs before puberty and after menopause.

In some people, hidradenitis suppurativa makes up one part of follicular occlusion syndrome, when it is associated with acne conglobata, dissecting cellulitis and pilonidal sinus. Hidradenitis suppurativa is also associated with Crohn disease.

Rare genetic autoinflammatory syndromes have been described in which hidradenitis suppurativa is a prominent features. Abnormalities of the PSTPIP1 gene on Chromosome 15q24-q25.1 are described (see PAPA syndrome).

What are the signs and symptoms of hidradenitis suppurativa?

The extent and severity of hidradenitis suppurativa varies widely between individuals. Initially, a firm pea-sized papule or nodule (0.5–1.5 cm diameter) may appear on one site, eg the armpit or groin. It may resemble an acne pimple. These lesions may resolve spontaneously, or, within hours to days, they may rupture and ooze a pus-like discharge. The nodules may heal without treatment. At a later time new lesions recur in the adjacent area and may include larger nodules, pseudocysts and abscesses, sinus tract formation, and involvement of multiple sites.

Hidradenitis suppurativa may spread to involve both armpits, on and under the breasts, the nape of the neck, waistband and inner thighs. Anogenital involvement most commonly affects the groin, mons pubis, vulva (in females), sides of the scrotum (in males), perineum, buttocks and perianal folds. The abscesses and sinus tracts can be painful.

How is severity and extent of hidradenitis assessed?

Severity and extent of a disease should be recorded at assessment and when determining the impact of a treatment. Photography of affected areas can also aid follow-up. Two scoring systems are in common use: Hurley Stages and Sartorius Hidradenitis Suppurativa Score.

Hurley Stages

The Hurley system describes three distinct clinical stages.

Sartorius Hidradenitis Suppurativa Score

The Sartorius Hidradenitis Suppurativa Score is made by counting involved regions, nodules and sinus tracts.


The six-point Physician Global Assessment (PGA) ranges from clear to very severe. It is used in clinical trials to measure clinical improvement in inflammatory nodules, abscesses and draining fistulae.


The Hidradenitis Suppurativa Clinical Response (HiSCR) is defined as a ≥ 50% reduction in inflammatory lesion count (abscesses + inflammatory nodules), and no increase in abscesses or draining fistulas when compared with baseline. It has been recently used to assess the effectiveness of treatment with biologics.


It is also useful to consider the degree of pain, the number of flares, and the impact on daily life in hidradenitis suppurativa. The Cardiff Dermatology Life Quality Index or DLQI questionnaire is often used.

What factors are associated with severe disease?

Severe hidradenitis (Hurley Stage 3) has been associated with:

What is the treatment for hidradenitis suppurativa?

Medical management of hidradenitis suppurativa is difficult. The aim is to catch the disease in its early stages and treat and control these milder forms. Antibiotics are usual therapy (partly to eradicate secondary bacterial infection and partly for their anti-inflammatory action) and long courses may be necessary. Weight loss in obese patients and smoking cessation are recommended.

General measures

Medical management

Treatment is required long term in many patients, as hidradenitis is a chronic disease.

Surgical management

Related information


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Author: Vanessa Ngan, staff writer and Dr Amanda Oakley, Dermatologist. Updated June 2015.

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