Refractory wheezing in Chinese children under 3 years of age: bronchial inflammation and airway malformation

BACKGROUND Wheezing is a common symptom in early childhood. However, refractory wheezing is difficult to treat, and it may thus account for extensive use of medical resources. It is therefore important to improve our understanding of the pathophysiology of refractory childhood wheezing. METHODS In this descriptive study, we studied 156 children with refractory wheezing using fiberoptic bronchoscopy and bronchoalveolar lavage (BAL), and compared the results with a control group of 46 children with various pulmonary diseases but no wheezing. Etiology and cell classification were analyzed for each BAL sample. RESULTS Overall, 21.8 % of children with refractory wheezing had airway malformations including tracheomalacia, airway stenosis, and tracheal bronchus. The incidence of airway malformations increased to 31 % in infants under 12 months of age. A significant increase in neutrophil ratio and decrease in macrophage ratio were observed in BAL from children with refractory wheezing compared with controls. Pathogen infection led to a higher ratio of neutrophils in the wheezing group compared with controls. However, there were no significant differences in neutrophil ratios among children with various pathogen infections. Furthermore, children with refractory wheezing had a high rate of Mycoplasma pneumoniae infection. CONCLUSIONS Airway malformations might play an important role in children under 3 years of age with refractory wheezing, especially in infants under 12 months of age. Neutrophil-mediated airway inflammation was characteristic of refractory wheezing in children under 3 years of age. In addition, infections such as M. pneumoniae may aggravate airway inflammation and affect refractory wheezing.