Thank you for your recent inquiry.
Cough-variant asthma is a well-established diagnosis in the medical literature. I have copied below two abstracts which review this issue. In many instances, such patients suffer from eosinophilic bronchitis. They have no obstructive disease but do respond to asthma therapy. The entity of cough-variant asthma was described perhaps first in the 1970's or 1980's in a New England Journal article, and the concept was refined later by Brightling and associates, the author of the reviews noted below.
Thank you again for your inquiry and we hope this response is helpful to you.
Otolaryngol Clin North Am. 2010 Feb;43(1):123-30, x.
Cough due to asthma, cough-variant asthma and non-asthmatic eosinophilic bronchitis.
Desai D, Brightling C.
Department of Infection, Inflammation, and Immunity, University of Leicester, Institute for Lung Health, Glenfield Hospital, UK.
Among the most common causes of chronic cough are asthma (25%) and nonasthmatic eosinophilic bronchitis (10%). In asthma, cough may present as an isolated symptom, in which case it is known as cough variant asthma. Variable airflow obstruction and airway hyper-responsiveness are cardinal features of asthma, which are absent in nonasthmatic eosinophilic bronchitis. The presence of eosinophilic airway inflammation is a common feature of asthma and is a diagnostic criterion for nonasthmatic eosinophilic bronchitis. At a cellular level, mast cell infiltration into the airway smooth muscle bundle, narrowing of the airway wall, and increased interleukin-13 expression are features of asthma and not nonasthmatic eosinophilic bronchitis. In most cases, the trigger that causes the cough is uncertain, but occasionally occupational exposure to a sensitizer is identified, and avoidance is recommended. In both conditions, there is improvement following treatment with inhaled corticosteroids, which is associated with the presence of an airway eosinophilia and increased exhaled nitric oxide. Generally, response to therapy in both conditions is very good, and the limited long-term data available suggest that both usually have a benign course, although in some cases fixed airflow obstruction may occur
Lung. 2010 Jan;188 Suppl 1:S13-7. Epub 2009 Aug 8.
Cough due to asthma and nonasthmatic eosinophilic bronchitis.
Institute for Lung Health, Department of Infection, Inflammation and Immunity, University of Leicester, Glenfield Hospital, LE3 9QP, Leicester, UK, email@example.com.
Asthma and nonasthmatic eosinophilic bronchitis are among the most common causes of chronic cough, accounting for about 25 and 10% of cases, respectively. Chronic cough due to asthma may present in isolation in which case it is known as cough-variant asthma. Nonasthmatic eosinophilic bronchitis is characterized by the presence of eosinophilic airway inflammation in the absence of variable airflow obstruction or airway hyperresponsiveness. Both conditions share many immunopathological features with the exceptions to date of mast cell infiltration into the airway smooth muscle, increased IL-13 expression, and narrowing and thickening of the airway wall, which are features reserved to asthma. In most cases the trigger that causes the cough is uncertain. However, removal of potential triggers is important to consider, in particular with respect to occupational exposure to known sensitisers. In both conditions there is subjective and objective improvement following treatment with inhaled corticosteroids, which is associated with the presence of an airway eosinophilia. Whether eosinophilic inflammation is the cause of cough or an epiphenomenon is uncertain, but the failure of anti-IL-5 to modify cough in asthma has questioned a causal association. In asthma, beta-agonist theophylline, leukotriene receptor antagonist, and oral corticosteroid therapy improve cough. In noneosinophilic bronchitis, some patients require oral corticosteroids but the benefit of other additional therapies is unknown. In general, response to therapy in both conditions is very good and the limited long-term data available suggest that both usually have a benign course, although in some cases persistent airflow obstruction may occur.
Phil Lieberman, M.D.