Figure 1.

Schema of the PBB–bronchiectasis disease spectrum and clinical definitions. Severe acute lower respiratory infections (ALRI) early in life are associated with development of protracted bacterial bronchitis (PBB). PBB, chronic suppurative lung disease (CSLD), and radiographic-confirmed bronchiectasis share common clinical features but are different, overlapping diagnostic entities within a disease spectrum. All share the underlying mechanisms of airway neutrophilia, endobronchial bacterial infection, and impaired mucociliary clearance. ALRI is associated with an increased risk of developing PBB and, if left untreated, progression to PBB and bronchiectasis among a subset of patients. Early diagnosis and treatment are essential to preventing progression to bronchiectasis, which is initially reversible.