Kidney Involvement

Renal involvement is a frequent and severe complication of antineutrophil cytoplasmic autoantibody (ANCA)-associated vasculitides (AAV). It is generally characterized by a pauci-immune necrotizing and crescentic glomerulonephritis with a very rapid decline of renal function (rapidly progressive glomerulonephritis). Even though there are no qualitative differences in glomerular lesions in patients with granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA), chronic damage is usually higher in MPA (and/or P-ANCA-positive patients) than in GPA (and/or CANCA-positive patients). If untreated, necrotizing and crescentic glomerulonephritis has an unfavorable course leading in a few weeks or months to end-stage renal disease (ESRD). Serum creatinine at diagnosis, sclerotic lesions, and the number of normal glomeruli at kidney biopsy are the best predictors of renal outcome. Corticosteroids and cyclophosphamide or rituximab (with the addition of plasma exchange in the most severe cases) are the cornerstone of induction treatment of ANCA-associated renal vasculitis, followed by azathioprine (or methotrexate, mycophenolate, rituximab) for maintenance. Despite significant improvement in patient outcomes over the past decades, AAV still results in ESRD in a quarter of patients over 5 years. Relapse rates are significantly lower in patients on chronic dialysis. Patient survival on regular replacement treatment (RRT) does not differ between AAV and matched nondiabetic patients, while it is lower than that of glomerulonephritis. Patients with AAV who undergo kidney transplantation have a mortality not different from the matched control group of primary glomerulonephritides, and favorable transplant survival is similar to that of the matched control groups.