Acne pathogenesis: history of concepts.

From the first reliable descriptions of acne in the early 19th century, dermatologists recognized it as a disease of the pilosebaceous follicle. Until the middle of the 20th century, they hypothesized that seborrhoea, follicular keratosis and microorganisms could be individually responsible for the acne lesions. Inflammation was only regarded as the final and inescapable step of the acne process. Although the importance of these factors has been reevaluated, recent works still regarded them as mandatory. In the 1970s, the onset of isotretinoin dramatically improved acne management. It also provided great opportunities for a better understanding of the pathogenic factors of acne. This study analyzes their genesis and development from the seminal contributions until recent advances.