[The formation of skin barrier and defective barrier-associated skin diseases]

Since the discovery of loss-of-function mutations in filaggrin (FLG) gene in atopic dermatitis (AD) individuals, significant attention has been paid against the skin barrier as an initial starting point of atopic march. Although FLG is a significant cornification-associated gene, skin barrier formation is a complex process mediated by an array of genes with specific functions. In this article, the mechanism of physical skin barrier formation is reviewed in detail, focusing on specific gene functions and inherited disorders caused by genetic aberrations. Additionally, the mechanism of percutaneous sensitization with environmental allergens in association with FLG-deficiency is reviewed in order to clarify the link between defective skin barrier and atopic march. Finally, updated knowledge of psoriasis pathophysiology in connection with genetic defect in skin barrier is reviewed. This article would provide a novel opportunity to understand the allergic/autoimmune disorders from the viewpoint of non-classical immune cells.