Painful cysts on the sternal and left axillary regions that had worsened over the past 3 weeks prompted a 42-year-old man to seek medical care. He reported that similar lesions in the same distribution first arose when he was 25 years old, and they recur each year. He denied having cystic acne in adolescence. Robert Levine, DO, of Long Beach, NY, diagnosed hidradenitis suppurativa based on the history and clinical appearance of the lesions. Primarily a disease of adults, this disorder presents as tender, erythematous, nodulocystic lesions most commonly in the axillary, genital, and perianal areas. Rarely, sinus tracts and scarring may develop. Hidradenitis suppurativa is caused by recurrent bacterial infection of apocrine glands. It is associated with cystic acne vulgaris and occasionally with pilonidal sinuses and Crohn disease. Treatment of hidradenitis suppurativa involves oral antibiotic therapy, intralesional corticosteroid injections, and incision and drainage of refractory lesions. Intractable disease may require excision with or without skin grafting. This patient was treated with an injection of triamcinolone acetonide and a 6-week course of erythromycin.