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| Fig. 21.1 Numerous microcomedones and comedones in patient with acne. (Courtesy of the William L. Weston, M.D. Collection.) |
The pilosebaceous unit, made up of a follicle (pore), sebaceous gland, and a vellus hair, is the target organ affected in acne. The face, chest, and back are areas with the greatest concentration of pilosebaceous follicles, corresponding to the areas most commonly affected by acne lesions. The primary lesion of acne is the microcomedo. This is the result of obstruction of the sebaceous follicles by sebum and abnormally differentiated and desquamated keratinocytes that may produce large comedones (Fig. 21-1). The four main pathophysiologic factors in acne vulgaris are:
- Inflammation (recent evidence indicates that inflammatory events precede the hyperkeratinization of the follicle)
- Sebaceous gland hyperplasia with excess sebum production
- Altered follicular epithelial growth and differentiation
- Propionibacterium acnes colonization of the follicle
Theboutot D, Gollnick H, Bettoli V, et al: New insights into the management of acne: an update from the Global Alliance to Improve Outcomes in Acne Group,
J Am Acad Dermatol 60:S1–S50, 2009.
Smolinski KN, Yan AC: Acne update,
Curr Opin Pediatr 16:385–391, 2004.
