[Chronic cough and protracted bacterial bronchitis in children and adolescents].

Persistent cough is one of the most common reasons patients present to outpatient practices. Especially in children, chronic cough (>4 weeks) is a significant burden on the child and family. While in the past, the lower airways were considered sterile, the concept of a physiologic microbiome of the lower respiratory tract has increasingly emerged. Of the differential diagnoses of chronic cough, protracted bacterial bronchitis (PBB) is more common in otherwise (pulmonary) healthy children under 6 years of age. Tracheomalacia may primarily exist or be the result of mechanically straining coughing, whereas apart from a reduced alveolar phagocytosis, there is usually no systemic or local immune weakness. Instead, an activated innate immunity with increased gene expression of the interleukin-1β signaling pathway can be immunologically detected. Here too, it is difficult to differentiate between cause and effect of chronic inflammatory events. Today, PBB and non-CF bronchiectasis, i.e., bronchiectasis not caused by cystic fibrosis (CF), are two sides of a disease spectrum of suppurative lung diseases, thus, making consequent therapy and long-term pediatric pneumological support of children with chronic productive cough necessary.