Hidradenitis suppurativa (HS) is an inflammatory disorder characterized by chronic deep-seated nodules, abscesses, fistulae, sinus tracts and scars in the axilla, inguinal area, sub-mammary folds and perianal area. This disfiguring condition is accompanied by pain, embarrassment and a significantly decreased quality of life. Although the mechanism of HS has not been entirely elucidated, lesion formation is believed to center around follicular hyperkeratosis within the pilosebaceous-apocrine unit. Recent research has provided new insight into the role of cytokines in the pathogenesis of HS, helping to close some existing knowledge gaps in the development of this condition. The first article in this continuing medical education series reviews HS epidemiology, clinical presentation, and classification. We also provide an update on the most recent understanding of HS pathogenesis, including the central role of inflammatory cytokines as well as other contributing factors such as genetics, hormones, and pathogenic microorganisms.