Chronic rhinosinusitis in unified airway disease: Surfactant proteins as mediators of respiratory immunity

PURPOSE OF REVIEW: The aim of this review is to describe the co-occurrence of chronic rhinosinusitis (CRS) with other inflammatory illnesses of the lower respiratory system characterised by airway obstruction and hyperresponsiveness, such as asthma, cystic fibrosis (CF), and chronic obstructive pulmonary disease (COPD) in the context of the unified airway disease (UAD). We also sought to discuss the novel role of surfactant proteins as mediators of innate immunity in the sinonasal epithelium and their potential as therapeutic interventions. RECENT FINDINGS: Different epidemiological and physiological studies in CRS and asthma have outlined that there are common clustering patterns in the phenotypes/ endotypes of both diseases, reinforcing the notion of the UAD. Also, surfactant proteins A (SP-A) and SP-D have now emerged as novel innate immunity molecules in bacterial sinusitis and allergic fungal sinusitis patients, respectively. SUMMARY: CRS and asthma coexist and are interconnected. Therefore, management of CRS and asthma must be jointly carried out as one functional entity. SP-A and SP-D bridge the innate and adaptive immunity mechanisms of the sinonasal epithelium to bring together a wellorchestrated mechanism that effectively fights pathogens. The use of SP-A to ameliorate the innate immune responses in CRS is a new concept and is likely to lead to new horizons in CRS therapeutic regimens.