Airway inflammation as an assessment of chronic nonproductive cough

The possibility that a bronchial inflammatory process could be involved with a chronic nonproductive cough without other potential causes such as postnasal drip syndrome, bronchial asthma, gastroesophageal reflux, chronic bronchitis, bronchiectasis, or the use of angiotensin-converting enzyme inhibitors has not been clearly described. We investigated the possibility that a chronic nonproductive cough without other potential causes is associated with airway inflammation, and if this is so, what the relationship might be between this inflammation and the possible etiology of the cough.

Twenty-five adults with chronic nonproductive cough as an isolated symptom over a 3-week period, and 5 healthy control subjects were studied.

Clinical assessments, cough scores, methacholine challenges, allergy skin prick tests, and bronchoscopies for bronchial biopsies were performed. In the bronchial biopsies, the patients were divided into the following two subgroups: 21 patients who were infiltrated with eosinophils vs the healthy control group (median, 12.0 vs. 0.0 cells/mm(2), respectively; p < 0.01); and 4 patients who were infiltrated with lymphocytes vs the healthy control group (median, 84.5 vs. 22.0 cells/mm(2), respectively; p < 0.01). With the methacholine challenge test, 5 of the 21 eosinophil-infiltrated patients received diagnoses of cough-variant asthma, and the other 16 patients received diagnoses of eosinophilic bronchitis. In the lymphocyte-infiltrated group, all four patients received diagnoses of lymphocytic bronchitis.

These results suggest that a chronic nonproductive cough as an isolated symptom is associated with airway inflammation due to eosinophil and lymphocyte infiltration. The causes of the chronic nonproductive cough were eosinophilic bronchitis, cough-variant asthma, and lymphocytic bronchitis.