Hidradenitis suppurativa (HS) should not be classified as a primary infection; rather, it is a chronic, recurrent, scarring, inflammatory disease that affects the regions of the skin where apocrine sweat glands are present: the axillae, inguinal folds, suprapubic area, anogenital area, buttocks, areola, and under the female breasts.

HS appears after puberty, usually during the second or third decades of life.

It is seen mostly in young women and only rarely before puberty. HS in African-American women tends to be more severe.

Initially HS presents with nodules and abscesses that may be indistinguishable from furunculosis or common “boils” (Fig. 16.19).

Chronic HS is indicated by the appearance of sinus tracts, fistula formation, ulcerations, and, eventually, hypertrophic, rope-like linear bands of scars and dermal contractures (Fig. 16.20).

Characteristic multiple open comedones (“blackheads”) develop in long-standing cases.

Lesions recur, new lesions crop up, and old lesions scar in a frustrating, unrelenting process.

HS lesions are painful and tender and often become secondarily infected.

Menstrual flares are common.

Lesions may exude a serosanguineous or foul-smelling purulent material that may stain clothing.

Often HS is a cause of embarrassment and social isolation.

When multiple lesions are present with scars and sinus tracts, HS is easily distinguishable from other conditions.

The exact cause of HS is unknown. An autosomal-dominant inheritance has been described.

Traditionally, it had been considered a primary inflammatory disorder of the apocrine glands (and was sometimes referred to as apocrinitis or apocrine acne).

Currently, it is believed that primary event is poral occlusion of the hair follicle that leads to retention of secretory products, dilation, and subsequent rupture triggering inflammation. In fact, in most biopsy specimens the apocrine glands are intact and unaffected, and follicular occlusion (acne-like findings) are the constant finding. Inflammation of the apocrine glands and bacterial infection are apparently secondary events.

As noted in acne vulgaris, HS is influenced by hormonal fluctuations and symptoms often improve during the estrogen-elevation phases of the menstrual cycle and during pregnancy, and often flare during the postpartum period.

The most common area of involvement is the axillary area and groin and tends to be symmetric.

Lesions may also be seen on the perineum, infra-mammary areas, the buttocks, and, rarely, the neck and scalp.

The course of HS varies.

Some patients only have very mild disease that may be indistinguishable from chronic furunculosis.

There may be improvement with age or as more scar tissue develops. Spontaneous improvement has been reported after menopause.

Total spontaneous resolution is rare.