From atopic dermatitis to asthma: the atopic march.

OBJECTIVE: To examine the mechanisms whereby allergen exposure through the epidermis could initiate systemic allergy and predispose individuals to the development of 1 or more atopic diseases via the so-called atopic march.

DATA SOURCES: PubMed databases from 1950 to the present were searched for relevant articles pertaining to epidemiologic and genetic evidence of the progression of the atopic march.

STUDY SELECTION: Articles concerning pathophysiologic conditions that link atopic dermatitis, allergic rhinitis, and asthma were examined.

RESULTS: The data suggest that a sequence of atopic manifestations occurs, typically atopic dermatitis in infancy followed by allergic rhinitis and/or asthma in later stages. Reduced filaggrin expression is implicated as a major predisposing factor for atopy in multiple lines of evidence, including genome-wide analysis and microarray investigations. Other gene products have an important role. Cross-sectional and longitudinal studies provide preliminary epidemiologic support for the sequential development of allergic diseases.

CONCLUSION: The mechanisms by which allergen exposure through the epidermis can initiate systemic allergy and predispose individuals to atopic dermatitis, allergic rhinitis, and asthma have become clearer in recent years. Longitudinal studies of individuals carrying loss-of-function filaggrin gene mutations are needed to further define the risks associated with epidermal barrier dysfunction and potentially identify specific targets for barrier repair and prevention of atopic dermatitis and other atopic disease. The effects of preventive and treatment strategies have been inconsistent across studies, and further research is warranted before any definitive recommendations can be made.