Crescentic glomerulonephritis is characterized by a rapid and progressive loss of renal function associated with severe oliguria and signs of nephritic syndrome. The most common histological features are the presence of crescents in most of the glomeruli. The crescents are formed predominantly by the proliferation of the parietal epithelial cells and by the infiltration of leukocytes internal to the Bowman capsule.

The renal biopsy (PAS stain) shows multiple glomeruli with collapsed glomerular tufts and crescent-shaped masses of different stages. There are also globally sclerosed glomeruli, moderate interstitial fibrosis and tubular atrophy in the background. Some tubules show intratubular calcifications. Vessels show severe hyaline arteriolosclerosis and moderate arterial sclerosis.

The immunofluorescence microscopy shows no significant staining for immune complexes (IgG, IgM, IgA, or C3). Electron microscopy shows no immune-type electron-dense deposits.

Overall, this is a case of pauci-immune crescentic glomerulonephritis due to the lack of detectable anti-GMB antibodies or immune complexes by immunofluorescence and electron microscopy. As is seen in this patient, most patients with this type of crescentic glomerulonephritis have circulating antineutrophil cytoplasmic antibodies (ANCAs) that produce cytoplasmic or perinuclear staining patterns and are usually associated with vasculitis.