Pearls and pitfalls in the diagnosis of cough variant asthma.

Cough alone may sometimes be the sole presenting symptom of asthma. Patients experience cough without wheeze or shortness of breath and with normal baseline pulmonary function test results. These patients do, however, demonstrate bronchial hyperreactivity. They also respond to specific traditional asthma therapy. These patients are considered to have a specific asthma phenotype: cough variant asthma (CVA).In prospective studies of patients with chronic cough, an average of 25% have CVA. Patients have chronic cough, normal baseline pulmonary function tests, positive bronchial inhalation challenge results, and response to specific asthma therapy. What makes these patients cough is still unknown. The cough reflex is complex. The specific cause of cough in CVA may be similar to cough mechanisms seen in typical bronchial asthma.All therapies for typical bronchial asthma have been successful in controlling cough in patients with CVA. The overall prognosis of CVA is excellent, with most patients requiring chronic inhaled corticosteroid therapy.