ABSTRACT
DEFINITION AND CLINICAL FEATURES A common inflammatory disorder of the pilosebaceous unit characterized by excessive production of sebum and the presence of comedones, papules, pustules, and cysts. Lesions almost always occur on the face though the upper back and chest are involved in around 70% of cases. The condition usually starts in adolescence and its peak prevalence is between the ages of 14 and 19. However, acne may persist into adult life and may present first after the age of 25 (late onset acne). Increased production of sebum, hypercornification of the pilosebaceous ducts, and colonization with Propionibacterium acnes are
the skin a shiny appearance (138). Comedonal lesions (139) usually precede inflammatory lesions (140) by several years. In dark-skinned individuals, resolution of lesions may be followed by disfiguring long-lasting postinflammatory hyperpigmentation.
