Figure 1

First renal biopsy specimen. On the first biopsy the glomerulus is globally hypercellular, with numerous intracapillary mononuclear cells. A small artery has intimal thickening with scattered infiltrating mononuclear cells, together with segmental medial disruption and perivascular fibrosis, indicating vasculitis (hematoxylin and eosin). This renal vasculitis is characterized by segmental fibrinoid necrosis associated with 35% crescents. Diffuse mesangial endocapillary proliferation and inflammatory cells infiltration is observed as well, consistent with crescentic glomerulonephritis.