Background: Nowadays, the heterogeneity of chronic rhinosinusitis (CRS) has attracted extensive attention. The histological patterns and clinical characteristics may vary greatly in different areas and among different groups of people. Prior studies found a shift from the neutrophilic inflam-matory pattern to the eosinophilic inflammatory pattern in Asian cities. This study set out with the aim of investigating the changes that have occurred in the past 18 years of southern China and exploring the causes. Methods: Tissues, clinical, and demographic characteristics were obtained from 473 patients (91 in 2000-2001, 170 in 2010-2011, 212 in 2017-2018) who satisfied the criteria of diffuse (bilateral) chronic rhinosinusitis. The clinical characteristics, including the previous history of allergic rhinitis and asthma, and the major symptoms of rhinosinusitis, were collected. Formalin-fixed nasal tissue was obtained from each patient for calculating inflammatory cells. We also performed immuno-histochemistry to evaluate the expression levels of eosinophilic cationic protein (ECP), IgE, mye-loperoxidase (MPO), and other Type 1, Type 2, and Type 3 related inflammatory cytokines. Results: The comorbidity of asthma and atopic disease was higher in 2017-2018 compared to 2000-2001. The histological characteristics revealed a significant increase in tissue eosinophils and decrease in neutrophils in 2017-2018 as compared with 2000-2001. Meanwhile, the proportion of eosinophilic CRS (eCRS) increased significantly from 2000 to 2001 to 2017-2018 (P = 0.03). The tissue eosinophil increase was higher in overweight patients (Body Mass Index, BMI >= 24) as compared with non-overweight. There was an increasing trend of ECP, IL-13 and IL-17. Besides, IFN-gamma and TNF-alpha decreased. Conclusions: There was an eosinophilic shift of diffuse rhinosinusitis inflammatory pattern in southern China over the last 18 years. The proportion of eCRS and difficult-to-treat rhinosinusitis has steadily increased, which is associated with the increase of Type 2, Type 3 cytokines and the decrease of Type 1 cytokines. This study also provided firstly evidence of a strong relationship between overweight and eosinophil shift in the southern Chinese population.
