Muco-Obstructive Lung Diseases

To the Editor: The review article by Boucher (May 16 issue) 1 does not include a discussion of asthma as a muco-obstructive lung disease.In a subgroup of patients with asthma, clinically significant mucus plugging is detected on highresolution computed tomographic imaging.This condition is characterized clinically by severe airflow obstruction and a lack of response to both bronchodilators and systemic glucocorticoids. 2 Mucus-derived obstruction is an important asthma phenotype because it may predict more persistent obstruction than that which is usually encountered and involve a treatment approach that is similar to that for other mucoobstructive diseases.Furthermore, overall mucin concentrations have been found to be higher both in patients with stable asthma and in those with asthma exacerbations than in healthy persons, although the predominant mucin in patients with asthma is MUC5AC, 3 and goblet-cell hyperplasia has been associated with neutrophilic asthma, which shares many similarities with chronic obstructive pulmonary disease (COPD). 4 Finally, hypertonic saline, which is frequently used in patients with other muco-obstructive lung diseases, has been shown to increase ciliary clearance in patients with asthma and is an underused therapy in this population. 5