Clinical approaches towards asthma and chronic obstructive pulmonary disease based on the heterogeneity of disease pathogenesis.

Asthma and chronic obstructive pulmonary disease (COPD) are each heterogeneous disease classifications that include several clinical and pathophysiological phenotypes. This heterogeneity complicates characterization of each disease and, in some cases, hinders the selection of appropriate treatment. Therefore, in recent years, emphasis has been placed on improving our understanding of the various phenotypes of asthma and of COPD and identifying biomarkers for each phenotype. Likewise, the concept of the endotype has been gaining acceptance; an endotype is a disease subtype that is defined by unique or distinctive functional or pathophysiological mechanisms. Endotypes of asthma or COPD may be primarily characterized by increased susceptibility to type 2 inflammation, increased susceptibility to viral infections, bacterial colonization or impaired lung development. The 'Dutch hypothesis' is as follows: gene variants underlying particular endotypes interact with detrimental environmental stimuli (e.g. smoking, viral infection and air pollution) and contribute to the ultimate development of asthma, COPD or both. Novel approaches that involve multidimensional assessment should facilitate identification and management of the components that generate this heterogeneity. Ultimately, patients with chronic inflammatory lung diseases may be treated based on these endotypes as determined by the respective biomarkers that correspond to individual endotypes instead of on disease labels such as asthma, COPD or even asthma-COPD overlap syndrome (ACOS).