Chronic Cough Due to Nonasthmatic Eosinophilic Bronchitis

Abstract

OBJECTIVES Nonasthmatic eosinophilic bronchitis is a newly recognized cause of chronic cough. Our objective was to review the pathogenesis, natural history, diagnosis, and treatment of this condition. METHODS The current literature was reviewed using an Ovid MEDLINE and PubMed literature review for all studies published in the English language from 1963 to December 2004 using the medical subject heading term "eosinophilic bronchitis." RESULTS Nonasthmatic eosinophilic bronchitis is a common cause of chronic cough. It is characterized by the presence of eosinophilic airway inflammation, similar to that seen in asthma. However, in contrast to asthma, nonasthmatic eosinophilic bronchitis is not associated with variable airflow limitation or airway hyperresponsiveness. The differences in functional association are related to differences in the localization of mast cells within the airway wall, with airway smooth muscle infiltration occurring in patients with asthma, and epithelial infiltration in patients with nonasthmatic eosinophilic bronchitis. Diagnosis is made by the confirmation of eosinophilic airway inflammation usually with induced sputum analysis after the exclusion of other causes for chronic cough on clinical, radiologic, and lung function assessment. The cough usually responds well to treatment with inhaled corticosteroids. The dose and duration of treatment differ between patients. The condition can be transient, episodic, or persistent unless treated, and occasionally patients may require long-term prednisone treatment. CONCLUSIONS Further study of this condition may improve our understanding of airway inflammation and airway responsiveness, leading to novel targets for therapeutic agents for the treatment of both asthma and nonasthmatic eosinophilic bronchitis.