Improvement of peripheral neuropathy in a patient with antineutrophil cytoplasmic antibody-negative eosinophilic granulomatosis with polyangiitis by additional mepolizumab

Background Eosinophilic granulomatosis with polyangiitis (EGPA) is a vasculitis characterized by abnormally high eosinophils and frequent peripheral neuropathy. Mepolizumab is an approved therapy for EGPA, but its efficacy against peripheral neuropathy remains unknown. Case presentation A 41-year-old woman was admitted in the hospital with dyspnea and neuropathy. Ground glass opacity and infiltrative shadow in the bilateral lungs were evident on chest computed tomography images. Eosinophils were increased in serum, in bronchoalveolar lavage fluid (BALF), and in transbronchial lung biopsy, and bacteria were not detected in BALF. EGPA resulting in severe eosinophilic asthma, sinusitis, pulmonary infiltrates, and peripheral neuropathy was diagnosed. Prednisolone (50 mg/day) caused remission of eosinophilic pneumonia and sinusitis, but not peripheral neuropathy. During prednisolone tapering (7 mg/day, 10 months after treatment), eosinophils were increased, and peripheral neuropathy relapsed. The humanized anti-IL-5 antibody mepolizumab (300 mg) was initially administered, followed by prednisolone. Mepolizumab caused sustained peripheral neuropathy remission and effective prednisolone tapering. Conclusions Introduction of mepolizumab combined with prednisolone may improve peripheral neuropathy.