This biopsy was taken from a 58-year-old male with no significant past medical history, who presents with gross hematuria, serum creatinine of 2.5 mg/dl and a urine protein/creatinine ratio of 1.4 g/g. The biopsy shows segmental rupture of the capillary loops associated with fibrinoid necrosis of the glomerular tuft and cellular crescent formation (Fig 1 – Jones stain). Of note, no mesangial or endocapillary proliferation is present. Immunofluorescence (Fig 2) shows mesangial granular staining for IgA (3+), C3 (1+), kappa (2+) and lambda (3+). Electron microscopy (not shown) shows scattered mesangial electron-dense deposits. The differential diagnosis in patients with necrotizing and crescentic glomerulonephritis with IgA deposits includes an IgA-dominant infection-associated glomerulonephritis, a crescentic primary or another secondary form of IgA nephropathy (such as Henoch-Schönlein purpura), and an ANCA-associated glomerulonephritis superimposed on a preexisting/incidental IgA nephropathy. Clinicopathological correlation is essential to reach a definitive diagnosis when this pattern of glomerular injury is encountered.
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