ABSTRACT
This chapter discusses the origins of asthma heterogeneity and the principles of classification to yield asthma phenotypes, focusing in particular on the increasing utilization of multivariate mathematical techniques for this purpose. It reviews the currently accepted, important phenotypes of asthma and how they influence pathways for care. The chapter discusses the multidimensional complexity of asthma heterogeneity and the rationale of the strategies that are being developed to address this heterogeneity. The heterogeneity in asthma has two key elements: the existence of multiple pathological entities and the variable influences exerted by the environment on the individual’s genotype. Eosinophilic airway inflammation was one of the earliest recognized pathological characteristics of asthma. Although previously considered the primary pathological disturbance in all cases of asthma, noneosinophilic variants of asthma are now widely recognized. Consequently, eosinophilic asthma is more appropriately considered an important disease phenotype with distinct clinical properties.
