Frequent exacerbator-a novel endotype of pediatric asthma.

Asthma is a complex and chronic respiratory condition that affects both adult and pediatric populations. Several asthma endotypes have been described; they include endotypes characterized by TH2 cell inflammation, response to viral infection, and exposure to air pollution. Recent evidence has revealed a novel endotype of pediatric asthma, termed the frequent exacerbator (FE) endotype, which is characterized by recurrent exacerbations. In this review, we provide an overview of the FE endotype. We review its epidemiology, its definition, and its environmental and clinical associations. We also detail findings from recent molecular characterizations of a pediatric FE endotype, with a specific focus on airway gene expression studies. As asthma exacerbations drive mortality and economic burden associated with disease, understanding the factors leading to frequent exacerbations is an important step in development of novel therapeutics and treatment strategies.