A case of subarachnoid haemorrhage associated with MPO-ANCA-positive eosinophilic granulomatosis with polyangiitis, successfully treated with glucocorticoid, cyclophosphamide, and mepolizumab.

Subarachnoid haemorrhage (SAH) is a quite rare but serious central nervous system complication of eosinophilic granulomatosis with polyangiitis (EGPA). We report a case of myeloperoxidase antineutrophil cytoplasmic antibody-positive EGPA in which SAH developed during glucocorticoid induction pulse therapy for skin purpura, peripheral neuropathy, and rapidly progressive glomerulonephritis. In addition to high-dose glucocorticoid and intravenous cyclophosphamide, we administered mepolizumab, a humanised anti-interleukin-5 monoclonal antibody, and this resulted in remission of the SAH. Although the pathogenesis of SAH in EGPA is not fully understood, both necrotising vasculitis and eosinophilic inflammation are thought to be involved. In addition to prompt intensive immunosuppressive therapy, mepolizumab should be considered for SAH associated with EGPA.