The patient’s recurrent indurated nodules under her arms and other intertriginous areas, often draining pus, are consistent with a diagnosis of hidradenitis suppurativa (HS).
HS is a chronic inflammatory and suppurative skin condition that primarily involves the sweat glands.1 The most commonly affected sites are intertriginous areas that include the axillae, groin, and perianal and inframammary regions.2 Prevalence of this disorder ranges from 0.05% to 4.1% of the population with an onset from puberty to adulthood, usually at around 40 years of age.3 Its incidence is twice as high in women as men and is more common in Black individuals.4,5
While its pathogenesis is not fully understood, it’s believed that excess proliferation of keratinocytes contributes to occlusion, leading to plugging of hair follicle ducts. Hormones, smoking, and obesity may contribute to and exacerbate HS. Intertriginous areas are prone to friction, leading to inflammation and further clogging.
The inflammation evolves into a chronic foreign body-type granulomatous inflammation with the potential for rupture, tunneling, and draining sinuses, which, although malodorous, are sterile, separating HS from an infected abscess.5 The result is thick, dense, scarred tissue.
The diagnosis is clinical in nature, with the history and physical exam distinguishing it from other skin disorders. In addition to the recurring physical pain, there is the emotional distress and self-consciousness about the drainage, odor, and scarring. This particular patient said that she avoided wearing sleeveless shirts due to the lesions’ appearance.
Treatment is multifactorial. Smoking and obesity are contributory factors, so smoking cessation and weight loss are recommended. For very mild HS, topical clindamycin 1% twice daily may suffice, but usually, due to the amount of inflammation, oral antibiotics are the initial therapy. (The use of antibiotics is for their anti-inflammatory component, as the nodules and unruptured tracts are sterile.)
Doxycycline 100 mg twice daily is the usual starting systemic antibiotic. In more severe or resistant cases, a combination of clindamycin and rifampin 300 mg each twice daily is used. (Worth noting: Rifampin interacts with oral contraceptives and many of these patients are women of reproductive age.) Treatment length is usually long (10 to 12 weeks) and recurrence is common.3
Spironolactone 100 mg daily and metformin 1000 mg extended release daily, which reduces insulin resistance, may be helpful. Intralesional injections of 10 mg/mL of triamcinolone in sterile saline can relieve the painful inflamed tracts. Referral for biologic agents, including infliximab, may be needed in severe cases that do not respond to other measures. Although invasive, wide debridement of the diseased tissue can reduce the disease burden.6
This particular patient said that she’d stopped smoking 3 years earlier and would work on losing weight. She was prescribed topical clindamycin 1% lotion twice daily along with oral clindamycin and rifampin dosed as above for 3 months. She declined metformin and intralesional injections. At a follow-up appointment 3 weeks later, she was pleased with the decrease in inflammation and had only 1 remaining tender area of fluctuance. She again declined injections and planned to continue on her oral and topical antibiotics.
Photo courtesy of Daniel Stulberg, MD, FAAFP. Text courtesy of Derissa F. Raynold, MD, and Daniel Stulberg, MD, FAAFP, Department of Family and Community Medicine, Western Michigan University Homer Stryker, MD School of Medicine, Kalamazoo.