Successful use of avacopan in a case of ANCA-associated vasculitis with treatment-resistant medium-sized vessel involvement.

We report the case of a 75-year-old woman who presented with fever, right back pain, paresthesia in the right extremities, erythema, purpura, and nodules. She had previously initiated dialysis due to rapidly progressive glomerulonephritis and was transferred to our hospital. Imaging studies revealed multiple cerebral and splenic infarcts and hemorrhage encapsulating the right kidney, likely due to microaneurysms in multiple renal arteries. High MPO-ANCA titers were observed, and a skin biopsy revealed granulomatous inflammation affecting medium-sized vessels, leading to a diagnosis of granulomatosis with polyangiitis (GPA) and ANCA-associated vasculitis (AAV) involving medium-sized vessels. Treatment began with intravenous pulse steroid therapy (methylprednisolone 1000 mg/day) and subsequent oral prednisolone (PSL) 40 mg (about 0.8 mg/kg) and intravenous cyclophosphamide (IVCY) at 250 mg. While her symptoms improved, she developed severe infections, including candidemia and febrile neutropenia. Consequently, we combined PSL with the C5a receptor antagonist avacopan, which allowed for PSL tapering and stabilized her disease. This case is significant as no previous reports of avacopan's efficacy in AAV with medium-sized vessel involvement suggest its potential effectiveness in such cases.