[How acne vulgaris develops].

For the initiation of acne multiple factors are required from endogenous to exogenous sources. The morphogenesis of acne is well studied, and the principle steps are discussed in the paper. Acne is a disease of humans, developing in sebaceous follicles. The first step is a proliferation-retention hyperkeratosis in the infundibulum, thus forming a follicular filament, from which a microcomedo arises. Finally open and closed comedones appear. This sequence is not strictly followed, but quite typical. Androgen stimulation activates sebaceous lipogenesis. At this point propionibacteria colonize the follicle and comedones. At earlier or later stages of the comedo development inflammatory phenomena appear, ranging from subtle to severe. Depending on the amount of inflammation, scars may develop. There is an undisputable genetic component for the initiation of acne, as twin studies have shown. The or these genetic factors have not been determined yet. The inflammatory cascade is up-regulated by immunological factors. Exogenous factors, underestimated in the past, seem to play an important role as well, as epidemiological studies and recent publications from different investigators have shown. Nutrition, particularly hyperglycemic food and milk products, are directly involved in the pathogenesis of acne.