A disease of infundibulosebaceous units, especially infundibula, that may manifest itself solely as noninflammatory lesions, i.e., comedones and intact cysts, or as inflammatory lesions, i.e., papules, nodules, and pustules. The process may resolve without residua or with scars of different types, e.g., keloidal or atrophic, including cribriform. The condition usually affects adolescents, but may at times be seen in neonates and young adults.

Virtually every adolescent is affected by acne vulgaris, if only in a mild form. In adolescents and young adults it may persist for years, whereas in neonates it usually lasts for weeks or a few months. The most severe expressions of acne occur in males.