Chronic wet cough: Protracted bronchitis, chronic suppurative lung disease and bronchiectasis

The role of persistent and recurrent bacterial infection of the conducting airways (endobronchial infection) in the causation of chronic respiratory symptoms, particularly chronic wet cough, has received very little attention over recent decades other than in the context of cystic fibrosis (CF). This is probably related (at least in part) to the (a) reduction in non-CF bronchiectasis in affluent countries and, (b) intense focus on asthma. In addition failure to characterize endobronchial infections has led to under-recognition and lack of research. The following article describes our current perspective of inter-related endobronchial infections causing chronic wet cough; persistent bacterial bronchitis (PBB), chronic suppurative lung disease (CSLD) and bronchiectasis. In all three conditions, impaired muco-ciliary clearance seems to be the common risk factor that provides organisms the opportunity to colonize the lower airway. Respiratory infections in early childhood would appear to be the most common initiating event but other conditions (e.g., tracheobronchomalacia, neuromuscular disease) increases the risk of bacterial colonization. Clinically these conditions overlap and the eventual diagnosis is evident only with further investigations and long term follow up. However whether these conditions are different conditions or reflect severity as part of a spectrum is yet to be determined. Also misdiagnosis of asthma is common and the diagnostic process is further complicated by the fact that the co-existence of asthma is not uncommon. The principles of managing PBB, CSLD and bronchiectasis are the same. Further work is required to improve recognition, diagnosis and management of these causes of chronic wet cough in children.