A Case of Renal Limited Myeloperoxidase Anti-Neutrophil Cytoplasmic Antibody-Positive Vasculitis Treated with Maintenance Avacopan Monotherapy.

A 76-year-old woman was admitted with progressive renal function decline. A kidney biopsy was performed because of myeloperoxidase anti-neutrophil cytoplasmic antibody (ANCA; 333 IU/mL), proteinuria (1.21 g/d), and urinary erythrocyte sediment (10–19/high-power field). Renal-limited ANCA-positive vasculitis with pauci-immune necrotizing crescentic glomerulonephritis (ANCA-associated vasculitis, AAV) was diagnosed. Glucocorticoid therapy was started, and the patient responded well. About 1 year later, avacopan treatment was started and glucocorticoid therapy was discontinued. Avacopan did not normalize ANCA levels and did not make urinary findings negative. However, further progression of renal function decline is prevented. Factors attributed to the development of AAV in this case were investigated; AAV developed after the second dose of the COVID-19 vaccine and ANCA levels re-elevated after the fifth dose. This suggests that the COVID-19 vaccine may have contributed to the development of AAV in this elderly patient. Avacopan monotherapy has been shown to be effective as maintenance therapy to control the progression of renal failure although not sufficient for complete remission of AAV.