The name Hidradenitis Suppurativa (HS) implies that the disease involves collections of white blood cells or “pus” in and around sweat glands. However, our current understanding of HS is that it begins with blockage of hair follicles followed by inflammation and possibly infection of the associated sweat glands. The areas that are most commonly affected are the underarms (axillae), breasts, groins, pubic area, and buttocks where there is an abundance of apocrine glands. HS is included with a “family” of follicular occlusion diseases, some or all of which may occur in the same individual: severe acne, dissecting cellulitis of the scalp, and pilonidal cyst.
The primary skin lesion in all of the follicular occlusion diseases is a red acne papule or pustule that may evolve into a deep nodule or abscess that becomes painful and discharges blood and pus. In the case of HS, multiple nodules may become connected by sinus tracts that tunnel below the skin surface. Such lesions generally heal with scarring with blackheads at both ends of the scar. Sometimes they continue to drain for weeks or months. Even when they heal, they are prone to erupt again in the same location.
The average age of onset of HS is in the 20’s and 30’s. It is usually not seen in young children unless there is a strong genetic component. HS is three times more common in women than in men. Risk factors that increase the severity of HS are obesity, cigarette-smoking, and mechanical irritation such as skin-to-skin friction. The prevalence of HS in the population is estimated to be less than 1%. Moderate to severe cases of the disease may affect only about 0.1% of the US population.
Conventional treatments for HS include antibacterial soaps, topical antiseptics and antibiotics as might be used for acne or folliculitis, incision and drainage of boils and abscesses, sometimes followed by local injections of corticosteroids. Chronic courses of oral antibiotics such as minocycline, doxycycline, clindamycin, and metronidazole may be used in more resistant cases.
In women, suppression of the male hormone effect might be achieved with oral contraceptives, estrogen supplementation, or the diuretic called spironolactone. The vitamin A derivatives called isotretinoin (Accutane) or acitretin (Soriatane) gave mixed results in studies, but positive effects were usually not long-lasting. The last two drugs should not be given to women of child-bearing potential because they have been associated with birth defects.
On September 11, 2015, the US Food and Drug Administration approved adalimumab (Humira), a tumor necrosis factor inhibitor, for the treatment of moderate to severe HS, making it the first FDA-approved drug for the disease. The move was based on studies in over 600 patients which showed significant reductions in total number of abscesses and inflammatory cysts with the drug compared to placebo.