Rosacea: part I. Introduction, categorization, histology, pathogenesis, and risk factors.

Rosacea is a chronic inflammatory skin condition that affects approximately 16 million Americans. Four distinct subtypes of rosacea have been recognized, with transient and nontransient facial flushing, telangiectasia, and inflammatory papules and pustules being among the more commonly recognized features. Although the exact pathogenesis of rosacea is unknown, dysregulation of the innate immune system, overgrowth of commensal skin organisms, and aberrant neurovascular signaling may all have a role in promoting the clinical features of rosacea.