Subclassification of chronic rhinosinusitis with nasal polyp based on eosinophil and neutrophil

OBJECTIVES/HYPOTHESIS: Japanese patients with chronic rhinosinusitis with nasal polyps (CRSwNP), differing from European and U.S. patients, are suggested to show two distinct phenotypes: Th2-polarized and Th1-shifted immunity. The purpose of this study was to conduct clinical subgrouping of CRSwNP based on inflammatory cell infiltration, which was evaluated and supported by clinical backgrounds and immunological characteristics. STUDY DESIGN: A cross-sectional study. METHODS: One hundred thirty Japanese patients with CRSwNP were classified by the infiltration of eosinophils and neutrophils in nasal polyps. Immunohistochemical analysis was performed in 42 patients. RESULTS: The patients were classified into three groups: 1) 42 patients with eosinophilic type, 2) 27 patients with neutrophilic type, and 3) 61 patients with noneosinophilic nonneutrophilic type. Both the number of serum eosinophils and the recurrence rates were significantly higher in the eosinophilic group compared to the other two groups. The IgE value was significantly higher in the eosinophilic group, followed by the noneosinophilic nonneutrophilic and neutrophilic groups. Both the symptomatic and CT scores were significantly greater in the eosinophilic group than in the neutrophilic group. The expressions of eotaxin, IL-17A, MUC5AC, and CD68 were greater in the eosinophilic group than in the other two groups. CONCLUSION: The eosinophilic CRSwNP phenotype is clinically characterized by serum eosinophilia, atopy, extensive disease, and poor prognosis compared to the neutrophilic and the noneosinophilic nonneutrophilic groups. We clearly demonstrated that all three subgroups of CRSwNP had characteristic differences in those inflammatory markers, which allows for pathophysiologically meaningful differentiations with likely therapeutic consequences.