Inflammatory phenotypes in asthma pathogenesis

Despite its prevalence and cost to the healthcare system, the pathogenesis of asthma remains poorly understood. It is clear that asthma is a heterogeneous disease and recent approaches have attempted to define asthma subgroups based on inflammatory phenotypes. Characteristics of the cellular makeup of sputum, blood, bronchoalveolar lavage fluid, and endobronchial biopsies have been examined in asthmatic subjects, with a primary focus on eosinophils and neutrophils, and, more recently, mast cells. The inflammatory phenotypes identified to date include eosinophilic asthma, neutrophilic asthma, pauci-granulocytic asthma, and T helper 2-associated asthma. Defining these phenotypes has already led to more personalized and successful targeted therapies, with new developments on the horizon.