In hidradenitis suppurativa (HS), painful, tender, erythematous, nodular lesions appear in the axillary, genital, and perianal areas (Fig. 53-1). Open comedones and patulous follicular orifices in and about the inflammatory areas are hallmarks of the disease. HS usually begins at a single site, but eventually appears in other apocrine gland-bearing areas as well. In severe cases, the buttocks, thighs, periumbilical areas, nipples, and scalp may be involved. Nodules suppurate, point, rupture, and drain pus, blood, and serous exudates. Sinus tracts form. Scarring is prominent. The disease progresses in fits and starts. HS is due to recurrent bacterial infection of apocrine glands (apocrine acne) and is primarily a disease of young adults. HS is sometimes associated with cystic acne vulgaris, occasionally with pilonidal sinuses or with Crohn’s disease.