Bronchiolitis is an acute viral illness affecting the lungs that causes inflammation of the lining of the epithelial cells in the bronchioles. This inflammation causes mucous production, inflammation and cellular necrosis of the epithelial cells. In addition, the cell inflammation can obstruct the airway with wheezing ultimately occurring. “It is the most common lower respiratory tract infection in children younger than 2 years of age” (Erickson et al., 2021). The respiratory syncytial virus is the most common cause of this illness. According to Erickson et al., (2021), RSV is an enveloped, non-segmented, negative strand RNA virus belonging to the paramyxovirus. Regarding the pathophysiology aspect, numerous processes occur.
The host’s inflammatory response contributes to the pathophysiology and symptomatology. Host cells recognize RSV via toll-like receptors, and secrete inflammatory cytokines (e.g. IFN-y, IL-1B, IL-4, IL-8). These effectors influence the local tissue environment directly, and also further the inflammatory process by drawing immune cells from the periphery. Many cytokines have known roles in the pathogenesis of RSV bronchiolitis, and some are even implicated in sustaining the infection. For example, the helper T cell’s main cytokine, IL-17, enhances RSV infection by increasing mucus production, inhibiting CD8 T cell activation, and reducing viral clearance. (Jacobson & Van Meer, 2013, p. 56).
Bronchiectasis is a permanent and abnormal widening of the bronchi due to chronic airway infection and inflammation and is a permanent condition. In addition, it can be localized to one lung or generalized to both. This disease can occur in young children and the elderly and people with COPD, immune dysfunction, rheumatoid arthritis, cystic fibrosis and other inflammatory conditions. “The dominant cell types involved in the inflammatory process in bronchiectasis are neutrophils, lymphocytes and macrophages” (King, 2009, p. 414). According to Shrawi et al., (2006), there is usually an initial event, which causes impairment of the mucociliary clearance of the bronchial tree, and the respiratory tract becomes colonized by bacteria that inhibit the ciliary function and promote further lung damage. In regard to the pathology of this disease, a combination of factors perpetuates this disease. “There is typically a defect in host defense, or some form of impaired drainage and/or obstruction within the airway walls that combines with a perpetuating infectious process that begets inflammation, and activates immune responses, proteolytic and oxidative processes” (Butler and Keane, 2017, p. 249).
In comparison, both bronchiolitis and bronchiectasis have similar attributes. Both illnesses affect young children and older adults due to a decreased or impaired functioning of the immune system. In addition, both produce a cough and inflammation in the lungs causing epithelial tissue damage that in turn causes obstruction of the small airways. In contrast, bronchiolitis is the most common in children two years of age or younger and is not a permanent infection. On the other hand, bronchiectasis results in a chronic obstruction of the small airways in the lungs resulting in a widening of the bronchi and a progressive decline in lung function. Bronchiectasis is preceded by other underlying chronic conditions for which no cure is available such as COPD and cystic fibrosis.
Butler, M W., & Keane, M. P. (2017). Bronchitis, bronchiectasis. Infectious Diseases, 243-250. https://doi.org/10.1016/B978-0-7020-6825-8.00027-7
Erickson, E. N., Bhakta, R. T., & Mendez, M. D. (2021). Pediatric Bronchiolitis. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK519506/
Jacobson, D., & Van Meer, A. (2013). Bronchiolitis. Journal of Maternal Fetal Neonatal Medicine, 2, 55-59. https://www.ncbi.nlm.nih.gov/pubmed/24059554#
King, P. (2009). The pathophysiology of bronchiectasis. International Journal of Chronic Obstructive Pulmonary Disease, 4, 411-419. https://doi.org/10.2147/copd.s6133
Shirawi, N. A., Jahdali, H. A., & Shimemeri, A. A. (2006). Pathogenesis, etiology and treatment of bronchiectasis. Annals of Thoracic Medicine, 1(1), 41-51. https://doi.org/10.4103/1817-1737.25870