Differential diagnosis of chronic cough in children.

A cough is considered chronic when it lasts >4 weeks. Chronic cough can be from a variety of causes. This article provides a structured approach to evaluating the child with chronic cough. Beginning with the disturbing cough that is absent once asleep, consistent with the habit cough syndrome, the diagnostic criteria for 10 causes of chronic cough are discussed. Using a structured approach to the differential diagnosis, common and uncommon causes can be identified. Well-established causes of chronic cough, such as asthma, are likely to be well known to the reader, whereas more recently identified etiologies, such as protracted bacterial bronchitis, are presented in more detail. The differential value of flexible and rigid bronchoscopy and bronchoalveolar lavage for aiding in the differential diagnosis is included for those entities where their use is essential.