Solo Addition of Mepolizumab Turned Antineutrophil Cytoplasmic Antibody Negative and Achieved Glucocorticoid Discontinuation in a Patient with Eosinophilic Granulomatosis with Polyangiitis

The interleukin (IL)-5 inhibitor mepolizumab is beneficial in eosinophilic granulomatosis with polyangiitis (EGPA), and the inhibition of antineutrophil cytoplasmic antibody (ANCA) production has been suggested as a possible mechanism. We herein report a 78-year-old Japanese man with EGPA who received solo mepolizumab 300 mg twice for elevated ANCA levels, which led to subsequent glucocorticoid (GC) discontinuation after achieving remission. The patient was able to be freed from the adverse events associated with long-term GC treatment, and the sole addition of mepolizumab also proved that mildly elevated ANCA could be converted to a negative result, thus leading to GC discontinuation.