Mepolizumab therapy improves endomyocarditis in seropositive eosinophilic granulomatosis with polyangiitis.

Heart involvement with cardiac insufficiency is a cause of early death and is associated with poor prognosis in eosinophilic granulomatosis with polyangiitis (EGPA),1 a disease classified as antineutrophil cytoplasmic antibody-associated vasculitis. Although cyclophosphamide (CYC) is required to induce disease remission in the presence of cardiac insufficiency,2 there is wellknown dosage-related cardiotoxicity in addition to increased risks of infertility, infection, and malignancy.3 Limited efficacy with significant adverse effects of CYC therapy has prompted the search for effective and secure alternative therapeutics in EGPA. Eosinophils play a central role in the pathogenesis, and the activation and recruitment of these cells are mainly mediated by interleukin (IL)-5, a key therapeutic target in EGPA.4 Nevertheless, mepolizumab (MEP), an anti-IL-5 monoclonal antibody, has been suggested in the induction treatment of EGPA with nonsevere diseases, such as asthma and sinonasal manifestations.5 Herein, we report a case of EGPA endomyocarditis with cardiac insufficiency under MEP induction therapy, leading to normalized cardiac dysfunction and disease remission with sparing use of glucocorticoids (GCs).