Atopic dermatitis is a common, chronic inflammatory
skin disease that is characterized by skin barrier dysfunction,
inflammation and intense itch. Although the exact mechanisms behind its pathogenesis remain unclear, it is evident that the complex interplay among barrier dysfunction,
inflammation and itch are critical in its development, progression and chronicity. Abnormalities in
filaggrin, intercellular
lipids and tight junctions induce barrier-disrupted skin, which produces
thymic stromal lymphopoietin,
interleukin (IL)-25 and IL-33; these in turn promote skin
inflammation characterized by type 2 immune deviation. This
inflammation then downregulates the expression of
filaggrin in keratinocytes and exacerbates epidermal barrier dysfunction. Furthermore, various itch mediators/pruritogens produced during this inflammatory process can act directly on sensory nerves and cause itch. In this review, we summarize the basics and recent advances in our understanding of the pathophysiology of
atopic dermatitis focusing on three aspects: barrier dysfunction, skin
inflammation and itch.