Abstract
BACKGROUND: Eosinophilic chronic rhinosinusitis (ECRS) is characterized by intense eosinophil infiltration in nasal polyps (NPs), related to asthma comorbidity and elevated circulating eosinophil levels. The mechanism by which these systemic components affect type 2 inflammation in NPs is poorly understood. OBJECTIVE: We sought to evaluate the relationship between lung function and eosinophilia in chronic rhinosinusitis and assess whether ECRS reflects lower airway involvement and systemic eosinophilic inflammation. METHODS: We examined 198 patients with chronic rhinosinusitis. Lung function was assessed preoperatively using spirometry and fractional exhaled nitric oxide (Feno). Patients were classified into ECRS and non-ECRS groups on the basis of the Japanese Epidemiological Survey of Refractory Eosinophilic Chronic Rhinosinusitis score, and patients with odontogenic maxillary sinusitis (OMS) were included for comparison. mRNA expressions of inflammatory cytokines in NPs were measured by quantitative real-time PCR. RESULTS: FEV(1)/forced vital capacity ratio, predicted FEV(1)/forced vital capacity, and predicted maximum midexpiratory flow were significantly lower in the ECRS group than in the non-ECRS and OMS groups. Feno levels were significantly higher in the ECRS group. The Japanese Epidemiological Survey of Refractory Eosinophilic Chronic Rhinosinusitis score correlated with lung function and Feno. Notably, some patients with ECRS showed impaired respiratory function and elevated Feno levels without a documented asthma diagnosis, suggesting possible undiagnosed asthma. Gene expression levels of type 2 cytokines in NPs were elevated in patients with ECRS and in those with peripheral eosinophilia greater than 5%. CONCLUSIONS: Respiratory function was significantly lower in patients with ECRS without an asthma diagnosis compared with non-ECRS and OMS groups. Enhanced eosinophilic inflammation in NPs may affect the lower airways, suggesting an eosinophilic united airway disease.