Eosinophilic bronchitis: an important cause of prolonged cough

The recent development of noninvasive techniques to measure airway inflammation has led to the recognition of eosinophilic bronchitis, a condition characterized by a sputum eosinophilia identical to that seen in asthma, but without any of the functional abnormalities associated with asthma. The condition is interesting for a number of reasons. Firstly, eosinophilic bronchitis is a common cause of chronic cough, which is important to recognize as it responds well to corticosteroids. However, recognition is not straightforward because it requires assessment of airway inflammation. Secondly, the natural history of eosinophilic bronchitis is uncertain. Some patients with chronic obstructive pulmonary disease without a history of previous asthma have sputum eosinophilia, thus one possibility is that eosinophilic bronchitis may develop into fixed airflow obstruction. Finally, the difference in the association of eosinophilic airway inflammation to airway dysfunction between eosinophilic bronchitis and asthma is of interest as it is possible that it reflects important differences in the nature or site of the airway inflammation. Further study of this interesting condition may shed light on the relationship between airway inflammation and airway responsiveness, leading to a greater understanding of both eosinophilic bronchitis and asthma.