KANAZAWA, JAPAN—Because nearly 30% of patients with cough-variant asthma develop full-blown asthma, the condition is considered an asthma precursor. It is not known, however, whether atopic cough also forewarns of asthma.

To investigate this issue, Masaki Fujimura, MD, and colleagues retrospectively compared outcomes for 82 patients with atopic cough and 55 patients with cough-variant asthma. During follow-up, typical asthma developed in one and eight patients, respectively, prompting the conclusion that atopic cough is not an asthma precursor.[1]

This finding expands earlier research comparing the pathophysiologic features of atopic cough and cough-variant asthma. “We found that these features are different between the two conditions, leading us to propose that atopic cough be recognized as a new clinical entity,” related Dr. Fujimura, who heads the Division of Respiratory Medicine at the Kanazawa Graduate University School of Medicine.

Atopic cough, he noted, is marked by eosinophilic tracheobronchitis without eosinophils in bronchoalveolar lavage fluid and by cough receptor hypersensitivity without bronchial hyperresponsiveness. Atopic cough is typically nonproductive.

By contrast, cough-variant asthma is similar to typical asthma; patients have mild bronchial hyperresponsiveness and eosinophilic airway inflammation. It generally responds to bronchodilator therapy, whereas atopic cough does not.

DIAGNOSIS, FOLLOW-UP, AND STEROID USE

The patients in the atopic cough group in Dr. Fujimura’s study ranged in age from 14 to 44; their median follow-up was 4.8 years. Three patients in this group received long-term inhaled corticosteroid therapy with beclomethasone.

The patients in the cough-variant asthma group ranged in age from 15 to 46 and were followed for a median of 3.7 years. Thirty-five of these patients were treated with long-term inhaled beclomethasone. A total of 67 patients from both groups were seen regularly at Kanazawa University Hospital and two related hospitals.

A SIGNIFICANT DIFFERENCE

The difference in asthma incidence between the two groups during follow-up was statistically significant. The analysis produced similar results when it was limited to Dr. Fujimura’s patients. Indeed, typical asthma did not develop in any of his 30 atopic cough cases, whereas it did in eight of his 37 cough-variant asthma patients.

An interesting finding was observed in the patients with cough-variant asthma. Typical asthma developed in only two of the patients who used beclomethasone but in six of the other 20 patients. Inhaled corticosteroids may therefore prevent the development of typical asthma in patients with cough-variant asthma, suggested Dr. Fujimura.

Although inhaled and oral corticosteroids are effective for atopic cough, azelastine is the first-line treatment for the condition as it is successful in 60% of cases, he related. The one patient with probable atopic cough who developed asthma had been treated successfully with azelastine for many years. None of the patients with definite atopic cough developed asthma despite receiving beclomethasone. n

—Timothy Begany