A pathogenic triad in chronic cough: asthma, postnasal drip syndrome, and gastroesophageal reflux disease.

BACKGROUND Coughing may be produced by a number of different disorders in distinct anatomic sites. Chronic cough causes major functional limitation in a considerable patient population and requires careful evaluation. METHODS Seventy-eight nonsmoking patients of both genders who complained of cough for > or =3 weeks and had normal findings on plain chest radiographs were studied prospectively. Their histories were obtained, and physical examinations were performed. The diagnostic workup included pulmonary function tests, CT of the paranasal sinuses and chest, carbachol provocation test, fiberoptic rhinoscopy, fiberoptic bronchoscopy, and 24-h esophageal pH monitoring. The final diagnosis depended on clinical, radiologic, and laboratory findings; a successful response to therapy was required for confirmation. RESULTS The causes of chronic cough were determined in all patients. Coughing was due to a single cause in 30 patients (38.5%) and multiple causes in 48 patients (61.5%). The five most important causative factors were asthma (46 patients; 58.9%), postnasal drip syndrome (PNDS; 45 patients; 57.6%), gastroesophageal reflux disease (GERD; 32 patients; 41.1%), bronchiectasis (14 patients; 17.9%), and tracheobronchial collapse (11 patients; 14.1%). INTERPRETATION Asthma, PNDS, and GERD, alone or in combination, were responsible for 93.6% of the cases of chronic cough. The presence of these three conditions was so frequent that the expression "pathogenic triad of chronic cough" should be acknowledged in specialized literature. It is essential to consider pulmonary and extrapulmonary causes in order to prescribe a successful specific therapy for chronic cough.