Disruption of airway lymphatics as a novel cause of impairment of airway clearance in severe asthma

Background We previously reported the phenotypic distribution patterns of airway smooth muscles in severe asthmatics; with smooth muscle bundle thickening only in large airways and in whole airways [1] , by different mechanisms, hypertrophy and/or hyperplasia [2], which was reexamined recently to fit in 55 fatal asthmatics by James AL, et al. [3]. We also revealed that pulmonary lymphatics distributed in interlobular septa and subpleural lesions were destroyed by increased fibrosis in patients with idiopathic pulmonary fibrosis which would impair alveolar clearance [4] . In this context, we were interested in the alteration of airway lymphatics in severe asthmatics and hypothesized that increased smooth muscle bundles and fibrosis in the airway walls would disrupt airway lymphatics and impair airway clearance in these patients.