Asthma phenotypes.

The many roads leading to the syndrome of asthma have proven to be intricately interconnected. The chronic inflammation of asthma is characterized by airway hyperreactivity and variable reversibility. Past classification systems relied on assessment of daily impairment and the distinction between intrinsic (nonallergic) and extrinsic (allergic). With more precise asthma phenotypes, association studies likely will have greater significance. In addition, patients at higher risk for severe disease can be more effectively managed, and treatments can be directed to responders. In this review, we look at eight identified phenotypes: atopic and nonatopic status, pre-asthma wheezing, inflammatory mediator predominance, aspirin-sensitive, exercise-induced, severe, and flare-prone asthma. Although significant overlap exists among the distinctions, any future phenotype classification system will need to incorporate these eight clinical asthmatic populations.