ANCA-Negative Pauci-Immune Glomerulonephritis: A Review

Background: Pauci-immune glomerulonephritis (PIGN) is typically secondary to antineutrophil cytoplasmic antibodies (ANCA) small-vessel vasculitis. However, some cases lack detectable circulating ANCA and are called ANCA-negative PIGN (seronegative PIGN). The reported incidence of this varies greatly. Its relationship to ANCA-associated vasculitis (AAV) is unclear. Summary: This review explores the pathophysiology of seronegative PIGN and summarizes findings from 12 studies focusing on this disease. The role of neutrophils appears to be central, with activation through cellular and humoral mechanisms. Most studies have noted less extrarenal involvement and more chronic changes in the kidney biopsy in seronegative PIGN compared to ANCA-positive cases. Studies have mostly reported using corticosteroids with cyclophosphamide for induction therapy and azathioprine for maintenance. The renal survival was noted to be lower compared to ANCA-positive PIGN. Key Messages: Whether ANCA-negative PIGN represents a distinct disease or is part of the AAV spectrum remains unclear. Prospective large-scale studies are needed to understand this disease for optimal diagnosis and management.