Bronchiectasis in severe asthma is associated with eosinophilic airway inflammation and activation

<b>Background:</b> Bronchiectasis is a common co-morbidity in severe asthma; however, the role of eosinophilic airway inflammation; a classic feature of asthma predominantly driven by IL-5 and IL-13; in bronchiectasis is unclear but association to disruption of the airway epithelium through eosinophil degranulation and increased mucus production is plausible. <b>Objective:</b> To describe the prevalence of bronchiectasis in an unselected population of patients with severe asthma, and the association with the airway eosinophilic inflammation and activation. <b>Methods:</b> In a cross-sectional design, all patients with severe asthma according to ERS/ATS criteria attending four respiratory clinics over a one-year period were included. All patients underwent HRCT and induced sputum was collected and analyzed for a cell-differential count, free eosinophilic granules (FEGs) and mRNA expression related to T2 inflammatory pathways. <b>Results:</b> Bronchiectasis was present in 31% of patients with severe asthma and half (52%) of these patients had airway eosinophilia whereas only 16% of patients without bronchiectasis had airway eosinophilia. Patients with bronchiectasis had a significantly higher sputum eosinophil count (5.3 vs. 0.8, p=0.001) as well as more extensive eosinophil degranulation, compared to those without bronchiectasis (13% vs 2%, p=0.05), suggesting a higher degree of eosinophil activation. We found increased expression of the IL-5 related gene CLC in patients with bronchiectasis (p=0.02). <b>Conclusion:</b> Bronchiectasis in severe asthma was associated with eosinophilic airway inflammation and eosinophilic degranulation and expression of IL-5 related genes.