The sounds of small airways: emerging role in pathogenesis and clinical expression of asthma

Asthma is a heterogeneous disease that involves a complex interplay of genetic and environmental factors,leading to chronic inflammation and airway remodeling.1,2 The major features that lead to clinical symptoms are infiltration of inflammatory cells,epithelial shedding,mucous gland hyperplasia,increased airway smooth muscle mass and contraction,and sub-epithelial fibrosis,which result in narrowing of the airways and obstruction.1-5 Over 100 years ago,studies used autopsy specimens to investigate the macroscopic morphological and histological changes and established the concept that inflammation was a major component of asthmatic pathology within the large airways.