Bronchiectasis

Abstract

Bronchiectasis is a disease characterized by irreversible bronchial dilatation caused by various etiologies, including chronic lung inflammation and recurrent infections. Inflammation is characterized by damage to the bronchial walls and frequent bacterial colonization. Although the prevalence of bronchiectasis has generally decreased in industrialized countries, it continues to be a problem in low and middle-income countries. The pathophysiology and pathogenesis of bronchiectasis, as well as the relationships between the variables that define the disease, its natural course, and response to treatment, are likely determined by the interaction between each patient's genetics and environment. Unfortunately, our current knowledge about the cellular, molecular, and genomic basis of bronchiectasis is still very limited. The condition can be limited to a single lung segment or can affect one or both lungs more extensively. Future research may involve the development of diagnostic imaging techniques that can utilize more of the information provided by high-resolution computed tomography scans (which is estimated to only utilize 1% of the information), the characterization and validation of biomarkers associated with the bronchiectasis clinical syndrome that can better characterize multiple endotypes (pathogenic mechanisms), and the expansion of biocomputing (computational capacity and artificial intelligence) that can process large amounts of data (big data). Previous respiratory tract infections, cystic fibrosis, immune deficiencies, and ciliary disorders are the most commonly identified causes; however, the cause is unknown in most cases. This demonstrates the interaction between immunogenetic susceptibility, immune dysregulation, bacterial infection, and lung damage. Damaged epithelium impairs mucus clearance and facilitates bacterial infection with increased cough, sputum production, and airflow obstruction. Bronchiectasis is most commonly seen in women and individuals over the age of 60, and its prevalence is increasing. Patients have daily excessive sputum and associated symptoms, recurrent chest infections, and impaired health-related quality of life. The interaction between inflammatory cytokines, transmural inflammation, mucosal edema, cavitation, ulceration, neovascularization in the airways, and immune effector cells (primarily neutrophils), reactive oxygen intermediates (e.g., hydrogen peroxide [H2O2]), neutrophilic proteases (elastase), and inflammatory cytokines results in bronchiectasis. Inflammatory blood proteins such as fibrinogen can serve as biomarkers for more severe disease. In industrialized countries, cystic fibrosis is the most common cause of clinically significant bronchiectasis. Other conditions associated with bronchiectasis include primary ciliary dyskinesia, foreign body aspiration, aspiration of gastric con tents, immune deficiency syndromes (especially humoral immunity), and infections (especially pertussis, measles, and tuberculosis). Bronchiectasis can also be congenital, such as in the case of Williams-Campbell syndrome, which involves the absence of ring-shaped bronchial cartilage, and Mounier-Kuhn syndrome (congenital tracheobronchomegaly), which involves connective tissue disorders. Other disease entities associated with bronchiectasis include yellow nail syndrome (lymphedema, pleural effusion, changing nail color) and middle lobe syndrome. Middle lobe syndrome presents in the early stages as persistent or recurrent infiltrations (pneumonia) of the middle lobe. Middle lobe syndrome is associated with other causes of bronchiectasis, including asthma, severe pneumonia, aspiration pneumonia, foreign bodies, cystic fibrosis, primary ciliary dyskinesia, and immune deficiency.