Differential diagnosis of chronic cough.

Coughing that lasts >3 weeks is generally considered chronic. The causes of chronic cough are many. Most often, chronic cough is due to postnasal drainage, asthma, and/or gastroesophageal disease. However, other causes such as laryngopharyngeal reflux, vocal cord dysfunction, occult sinusitis, pertussis, and angiotensin-converting enzyme inhibitor should be considered. Even rarer entities will be discussed as well as some of the pathophysiology associated with the cough reflex.