Bronchiectasis is a complex, heterogeneous disorder defined by both a radiological abnormality of permanent bronchial dilatation and a clinical syndrome. There are multiple underlying causes including severe infections, mycobacterial disease, autoimmune conditions, hypersensitivity disorders, and genetic conditions. The pathophysiology of disease is understood in terms of interdependent concepts of chronic infection, inflammation, impaired mucociliary clearance, and structural lung damage. Neutrophilic inflammation is characteristic of the disease, with elevated levels of harmful proteases such as neutrophil elastase associated with worse outcomes. Recent data show that neutrophil extracellular trap formation may be the key mechanism leading to protease release and severe bronchiectasis. Despite the dominant of neutrophilic disease, eosinophilic subtypes are recognized and may require specific treatments. Neutrophilic inflammation is associated with elevated bacterial loads and chronic infection with organisms such as Pseudomonas aeruginosa. Loss of diversity of the normal lung microbiota and dominance of proteobacteria such as Pseudomonas and Haemophilus are features of severe bronchiectasis and link to poor outcomes. Ciliary dysfunction is also a key feature, exemplified by the rare genetic syndrome of primary ciliary dyskinesia. Mucus symptoms arise through goblet cell hyperplasia and metaplasia and reduced ciliary function through dyskinesia and loss of ciliated cells. The contribution of chronic inflammation, infection, and mucus obstruction leads to progressive structural lung damage. The heterogeneity of the disease is the most challenging aspect of management. An understanding of the pathophysiology of disease and their biomarkers can help to guide personalized medicine approaches utilizing the concept of “treatable traits.”

支气管扩张是一种复杂的异质性疾病，其定义为永久性支气管扩张的放射学异常和临床综合征。有多种潜在原因，包括严重感染、分枝杆菌疾病、自身免疫性疾病、过敏性疾病和遗传疾病。疾病的病理生理学被理解为慢性感染、炎症、黏液纤毛清除受损和结构性肺损伤等相互依赖的概念。中性粒细胞炎症是该疾病的特征，有害蛋白酶（如中性粒细胞弹性蛋白酶）水平升高与较差的结果相关。最近的数据表明，中性粒细胞胞外陷阱的形成可能是导致蛋白酶释放和严重支气管扩张的关键机制。尽管中性粒细胞疾病占主导地位，嗜酸性亚型已被识别，可能需要特殊治疗。中性粒细胞炎症与细菌负荷升高和生物体慢性感染有关，例如铜绿假单胞菌。正常肺微生物群的多样性丧失和变形菌如假单胞菌和嗜血杆菌的优势是严重支气管扩张的特征并与不良结果有关。纤毛功能障碍也是一个关键特征，以罕见的原发性纤毛运动障碍遗传综合征为例。粘液症状通过杯状细胞增生和化生出现，并通过运动障碍和纤毛细胞损失降低纤毛功能。慢性炎症、感染和粘液阻塞导致进行性肺结构损伤。疾病的异质性是管理中最具挑战性的方面。了解疾病的病理生理学及其生物标志物有助于指导利用“可治疗特征”概念的个性化医疗方法。