Atopic dermatitis (AD) is a chronic, inflammatory skin disorder that affects up to 20% of children worldwide. AD has been highlighted as the first step in the “atopic march”, whereby AD typically predates the development of other allergic disorders. The population prevalence of asthma is ~10%, but it has been estimated that one-third to half of patients with AD will develop asthma. The mechanisms that promote disease progression from AD to asthma remain unclear. Although atopic sensitization and food allergy have been reported to be major determinants of AD progression to respiratory allergy, only about 3% of children follow the complete course of what has been conventionally referred to as the atopic march. However, early-life AD remains a major risk factor for the development of any atopic disease.
As part of our U19 Asthma and Allergic Diseases Cooperative Research Center (AADCRC) funded by the National Institute of Allergy and Infectious Diseases, we have built the first mechanistic longitudinal cohort study of pediatric atopic dermatitis (AD), the Mechanisms of Progression of Atopic Dermatitis to Asthma in Children (MPAACH).
MPAACH is the first early life prospective cohort of children with AD in the US and incorporates extensive evaluations of skin, gut, airway and peripheral blood, as well as the use of multiparameter approaches to define phenotypic and endotypic subgroups of AD. Thus far, we have enrolled 550 children. The goals of the MPAACH cohort are to define AD phenotypes and endotypes, dissect the mechanisms that contribute to the progression of AD to other allergic disorders (food allergy, allergic rhinitis, asthma), and delineate the immunologic, skin, biome, genetic/epigenetic/genomic, physiologic, and environmental factors that promote the development of allergic comorbidities in children with AD. To enable mechanistic studies, extensive biospecimens are collected from lesional and non-lesional skin.
Our overarching hypothesis is that visually normal skin may have skin barrier dysfunction that becomes clinically evident (lesional) or remains subclinical (no lesions), but in both cases the skin barrier dysfunction coupled with dysbiosis of skin microbiome triggers alarmins, which initiates an immunologic cascade that promotes the subsequent development of allergic disease including food allergy, asthma and allergic rhinitis.