Successful early introduction of mepolizumab for peripheral neuropathy with a peripheral circulatory disorder in a patient with myeloperoxidase anti-neutrophil cytoplasmic antibody-negative eosinophilic granulomatosis with polyangiitis

A 26-year-old woman presented with abdominal pain, diarrhoea, vomiting, fever, and progressive paralysis in the lower limbs. She had a history of bronchial asthma and experienced sinusitis, progressive peripheral neuropathy, polyarthritis, and leukocytosis with prominent eosinophilia. The patient was diagnosed with eosinophilic granulomatosis with polyangiitis (EGPA). Abdominal pain was considered to be an ischaemic enteritis associated with EGPA. She was administered 1,000 mg/day of methylprednisolone for 3 days and intravenous immunoglobulin (400 mg/kg/day of γ-globulin for 5 days) followed by 50 mg (1 mg/kg)/day of oral prednisolone due to rapidly progressing peripheral neuropathy. Her symptoms temporarily improved; however, peripheral neuropathy recurred after a week, and the eosinophil count increased. Eighteen days after following the resumed treatment, 300 mg of mepolizumab, a humanised monoclonal antibody, was administered. Subjective symptoms, nerve conduction velocity, and skin perfusion pressure (an index of peripheral circulation in the lower extremities) improved after 4 weeks. Although mepolizumab has been approved for EGPA, there is no evidence of its efficacy against peripheral neuropathy. Early introduction of mepolizumab may contribute to an the early improved progressive peripheral neuropathy with eosinophilia.