[Mechanisms and causes of acne].

Three pathogenic factors are closely involved in the mechanism of acne with a sequence beginning with seborrhea, then sebum retention, and finally inflammation. The sebaceous gland is a target of androgens. Acne may be related to an excessive sensitivity of sebaceous end-organs to androgens. However, in women, an ovarian or adrenal hyperandrogenism may be implicated. The cause of sebum retention is the hyperkeratinisation of the infra infundibulum of the sebaceous duct. Many factors, particularly the chemical composition of sebum in acne and the androgens are responsible for this hyperkeratinisation. The inflammation is related to the inflammatory role of the numerous enzymes of Propionibacterium acnes and to the chimiotactism of neutrophils. Other pathogenic factors may have a role in acne, particularly smoking and stress. The knowledge of these pathogenic factors and their evaluation in each patient are a main point for therapeutic strategy, because every available treatment has a special impact on such or such factor.