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Thursday, October 2, 2014

Complexities of atopic dermatitis

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease and often precedes the development of food allergy and asthma.  The defective skin barrier in AD is thought to allow the absorption of allergens through the skin.  This promotes systemic allergen sensitization, contributing to the development of food allergy and asthma, as well as skin infections such as Staphylococcus aureus and herpes simplex virus (HSV).  This month’s JACI focuses on the importance of both genetic and acquired causes of epithelial skin barrier dysfunction in driving the natural history of AD. In their review, Donald Leung and Emma Guttman-Yassky summarize current insights into AD that may lead to new treatment approaches, including several articles published in this month’s journal (J Allergy Clin Immunol 2014; 134(4): 769-779).

The causes of AD are complex and driven by a combination of genetic, environmental and immunologic factors which likely account for heterogeneity of AD onset, severity and natural history of the disease. While there is currently no cure for AD, recent studies suggest prevention of AD can be achieved by early interventions that protect the skin barrier such as emollients and topical anti-inflammatory treatments. Importantly, the control of lesional AD may improve long term outcomes not only in AD, but in allergic diseases of the gastrointestinal and respiratory tracts as well, due to the reduction of associated allergen sensitization.

Although current treatment options for AD are limited, the authors explain that in addition to Th2 antagonists (i.e. the anti IL-4R drug dupilumab), determining the key role of TSLP-receptor signaling and IL-22 that involve clinical trials with agents that target TSLP, Th22, and TH17/IL-23 will be of interest. Furthermore, the selection of therapeutics for patients with differing degrees of disease severity and /or phenotypes should be guided by defining the extent of activation in the skin and blood. For example, anti IL-23/IL-17 might provide beneficial responses particularly in intrinsic AD patients. The individual contributions of the TH22, Th17, and Th2 immune pathways to the disease phenotype will be clarified through clinical trials coupled with mechanistic studies that are currently in progress. This comprehensive review highlights the importance of translational medicine, from animal models to clinical trials, and how this approach is advancing AD research.

Questions for the authors:
Recently, both basic science and clinical research have provided novel insights into the prevention, identification, and treatment options for AD. Do you anticipate these findings to improve outcomes for not only AD but other allergic diseases as well?

Yes, because the principle underlying causation of allergic diseases likely have in common a defective epithelial barrier and abberant immune response.  This is modulated by different resident cells in each organ.

AD is most often a first step in a series of atopic diseases in the Atopic March that often leads to rhinitis, food allergy, and asthma. Could removing the first step in the Atopic March reduce the global burden of atopic disease? 

Possibly.  The studies in the current issue of JACI support the concept that skin barrier dysfunction enhances sensitization via environmental allergen exposure. A natural progression of this concept would be to correct the skin barrier defect to determine whether elimination of AD could prevent food allergy, asthma and allergic rhinitis.

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