Comparative characteristics of different endotypes in chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is the most common reason for consulting at the otolaryngologist. Although data on the prevalence of rhinosinusitis are inconsistent, the average global prevalence was 11.61±5.47%, ranging from 1.01% to a maximum of 57.6%. As based on the consensus document EPOS 2020 (European Position Paper on Rhinosinusitis and Nasal Polyposis), CRS is classified into polypous and polyp-free rhinosinusitis. Polypous rhinosinusitis is a special type characterized by inferior response to conservative therapy, and frequent relapses after surgical treatment. These serious medical and social issues are promoting the studies on pathogenesis and development of nasal polyps. This review provides information about immunological features and dysfunction leading to emergence of CRS with or without polyps. The purpose of this literature review is to evaluate the role of the first-line immune defense, congenital and acquired components of immunity in pathogenesis of polyposis versus nonpolypous CRS. The article provides a review of the research articles published worldwide. The authors conducted a search on the significance of immune response in development of CRS with and without polyps. We used appropriate keywords and filters in the PubMed and Google Scholar databases, in Scopus, Web of Science, MedLine, Cochrane Library, EMBASE, Global Health, and CyberLeninka databases. The detailed search has shown that all components of immune system do not fully perform their functions. E.g., the respiratory epithelium and mucociliary clearance present the first-line immune defense of nasal and sinus mucosa which form a mechanical barrier to infectious and other invading agents. At the next stage, the cells of innate immune response, along with complement system, take part in elimination of external pathogenic agents. Presentation of antigen epitopes to lymphocytes generates a specialized adaptive immune response. Tissue remodeling is among the most relevant aspects of the CRS pathogenesis. Production of periostin is found to be increased in polyposis rhinosinusitis, along with progressive tissue eosinophilia, higher production of cystatin SN, IL-25 and fibroblast contents, decreased TLR2, TLR4, TGF-β and collagen production as well as increased extracellular neutrophil traps and M1 macrophage levels. Further studies on the links in immune pathogenesis of CRS could allow us to develop a personalized algorithm for the diagnosis and treatment of such patients.