Atopic dermatitis (AD) is a recurrent, chronic, inflammatory, itchy skin
disorder that affects up to 20% of the pediatric population and 10% of the
adult population worldwide. Onset typically occurs early in life, and although
cardinal disease features are similar across all ages, different age groups and
ethnicities present distinct clinical characteristics. The disease imposes a
significant burden in all health-related quality of life domains, both in
children and adults, and a substantial economic cost both at individual and
national levels. The pathophysiology of AD includes a complex and multifaceted
interplay between the impaired dysfunctional epidermal barrier, genetic
predisposition, and environmental contributors, such as chemical and/or
biological pollutants and allergens, in the context of dysregulated T2 and
T17 skewed immune response. Regarding the genetic component, the loss of
function mutations encoding structural proteins such as filaggrin, a fundamental
epidermal protein, and the more recently identified variations in the epidermal
differentiation complex are well-established determinants resulting in an
impaired skin barrier in AD. More recently, epigenetic factors have facilitated
AD development, including the dysbiotic skin microbiome and the effect of the
external exposome, combined with dietary disorders. Notably, the interleukin
(IL)-31 network, comprising several cell types, including macrophages, basophils,
and the generated cytokines involved in the pathogenesis of itch in AD, has
recently been explored. Unraveling the specific AD endotypes, highlighting the
implicated molecular pathogenetic mechanisms of clinically relevant AD
phenotypes, has emerged as a crucial step toward targeted therapies for
personalized treatment in AD patients. This review aims to present
state-of-the-art knowledge regarding the multifactorial and interactive
pathophysiological mechanisms in AD.