Understanding the key issue in the diagnosis and treatment for Type 2 chronic rhinosinusitis

Abstract

The concept of chronic rhinosinusitis (CRS) has shifted from the traditional clinical classification of phenotypes, which are largely based on the presence or absence of nasal polyps, to three inflammatory endotypes (Types 1, 2, and 3), based on specific mechanisms and molecular biomarkers. Treatment based on their pathological mechanisms has also changed significantly. The typical disease of Type 2 inflammatory CRS is eosinophilic CRS (ECRS), which has a characteristic clinical presentation different from that of previous bacterial CRS. Type 2 CRS and non-Type 2 CRS differ greatly, not only in their primary site of involvement but also in the cytokines and inflammatory cells involved in their pathogenesis. Therefore, even the conservative treatment methods and ESS (Endoscopic sinus surgery) techniques differ substantially between Type 2 and non-Type 2 CRS. Previous reports indicate that approximately half of all CRS cases involve Type 2 inflammation. When other endotypes are combined, 72％ of CRS cases are associated with Type 2 inflammation, and 87％ of CRS with nasal polyps are associated with Type 2 inflammation. The number of cases of eosinophilic sinusitis is increasing in Japan, and the number of uncontrolled CRS patients is also increasing under conventional classical treatment. This paper describes the pathogenesis of Type 2 inflammatory CRS, represented by ECRS, and discusses approaches to its diagnosis and treatment. In addition, steroid therapy, including the results of treatment in our institution, ESS methods, and biologic agents for Type 2 CRS, are also discussed.