An uncommon histologic pattern of anti-GBM glomerulonephritis; focal crescentic and necrotizing pattern

Anti-glomerular basement membrane (anti-GBM) disease is a rare small-vessel vasculitis that involves glomerular capillaries, pulmonary capillaries or both, with anti-GBM autoantibody deposition along the GBM. It typically presents with alveolar hemorrhage and rapidly progressive crescentic glomerulonephritis that progresses abruptly to end-stage renal failure if untreated. Autoantibodies targeting the alpha-3 chain of type IV collagen mediate the disease in glomerular and alveolar basement membranes. Histologically, the kidneys generally display diffuse necrotizing and crescentic glomerulonephritis. This case report highlights the case of a 20-year-old man who was admitted with a working diagnosis of pulmonary renal syndrome. His anti-GBM antibodies result came out at a level of 200 U/mL (normal level < 20 U/mL). The renal biopsy findings were unusual as it showed glomeruli with only 11% cellular crescents and 7% tuft fibrinoid necrosis. In addition, by immunohistochemical studies, the biopsy reveled a strong IgG and IgA signals by immunoperoxidase method, which is another unusual finding in the setting of anti-GBM glomerulonephritis. The final renal biopsy diagnosis was focal necrotizing and crescentic glomerulonephritis (with 11% cellular crescents) compatible with anti-GBM glomerulonephritis. This case demonstrates the paramount importance of clinicopathological correlation when interpreting medical renal biopsies.