Background: Dupilumab, prescribed for the treatment of poorly controlled chronic rhinosinusitis with nasal polyps (CRSwNPs), is associated with serious side effects. Notably, eosinophil levels in the peripheral blood may be elevated in some patients. In this study, we examined the detailed characteristics of hypereosinophilia during dupilumab therapy, and developed an algorithm for dupilumab administration.

Materials and Methods: This study included 27 patients with eosinophilic chronic rhinosinusitis (ECRS) that was poorly controlled with existing therapies. Blood tests were conducted at 2 and 24 weeks after dupilumab administration. The criterion for hypereosinophilia was a peripheral blood eosinophil count ≥ 1,500 cells/μl. This study investigated the trends in peripheral blood eosinophil counts associated with dupilumab administration, and the detailed course and response of patients with hypereosinophilia.

Results: Peripheral blood eosinophil counts (mean ± SD) at 2 and 24 weeks after the initiation of dupilumab treatment were 589.2 ± 269.4, 668.6 ± 548.4 and 581.3 ± 418.4, respectively, demonstrating no statistically significant increase; however, hypereosinophilia was observed in 2 patients. One patient developed eosinophilic pneumonia and continued dupilumab treatment with systemic steroid administration.

Conclusion: Eosinophilia (≥1,500 cells/μl) in peripheral blood during dupilumab administration was observed in 2 of 27 patients (7.4%). Based on these results, the present study provides an algorithm for the management of eosinophilia in peripheral blood during dupilumab treatment.