A Case of Eosinophilic Granulomatosis with Polyangiitis with Severe Peripheral Neuropathy Refractory to Standard Treatment SuccessfullyTreated by Mepolizumab

The clinical benefits of administering mepolizumab to patients with Eosinophilic Granulomatosis with Polyangiitis (EGPA) to prolong the remission period have recently been reported. However, the timing of initiating mepolizumab and the clinical characteristics that are best indicators for mepolizumab treatment have not yet been identified. Herein, we report the case of a 57-year-old male Japanese patient with Anti-Neutrophil Cytoplasmic Antibody (ANCA)-negative EGPA who manifested severe peripheral neuropathy refractory to standard therapy. The patient was administered with a high-dose steroid, intravenous cyclophosphamide, intravenous immune globulin, and finally mepolizumab, which resulted in the clinical improvement of nervous symptoms without any adverse effects. Clinicopathologically, ANCA-negative peripheral neuropathy might be caused by eosinophil-associated vascular occlusion, leading to ischaemia, toxic protein release, and, ultimately, tissue damage. Therefore, this case indicates that using mepolizumab for patients with early-phase EGPA might be clinically beneficial, especially in cases of ANCA-negative EGPA with peripheral neuropathy.