The glomerulus shows marked, diffuse hypercellularity. The increase in cellularity is due to neutrophils and to proliferation of endogenous endothelial cells and mesangial cells. A few neutrophils are noted in the urinary space. The immune complexes are presumed to form in situ in the glomeruli due to previously planted streptococcal antigen. Immune complexes form in situ in glomeruli due to previously planted streptococcal antigens.
Most cases are in the pediatric age group.
Streptococcal infections are the most common, but other infectious agents are capable of producing the disease. The kidneys in postinfectious glomerulonephritis may show no particular gross abnormalities. In severe cases, the cut surface of the renal cortex may show a petechial or flea-bitten appearance. The glomeruli are diffusely and globally hypercellular with a predominance of neutrophils. The increased cellularity is endocapillary, meaning that the increase in cells is within the glomerular tuft and there is little if any proliferation of cells in the urinary space.