Atopic dermatitis: pathogenetic mechanisms

Atopic dermatitis (AD) is a chronic inflammatory skin disease with increasi ng incidence and socio-economical relevance. The diagnosis is made on clini cal grounds and different diagnostic criteria sets have been established. T he majority of all AD cases is associated with a sensitization to environme ntal allergens and increased serum IgE (so-called extrinsic AD), but about 10-30% of all cases suffer from the so-called intrinsic AD, which obviously lacks any link to the classical atopic diathesis. The genetic background o f AD has been investigated by target gene approach by different groups with mostly contradictory results for each of the genes under study. An imbalan ce in the spectrum of Th1/Th2 responses, a disturbed prostaglandin metaboli sm, intrinsic defects in keratinocyte function, delayed eosinophil apoptosi s, IgE-mediated facilitated antigen presentation by epidermal dendritic cel ls, a two phase model of the inflammatory response and staphylococcal super antigen effects are among the currently studied pathogenetical aspects of e xtrinsic AD, which are reviewed in this paper.