Postinfectious glomerulonephritis
- Lesion
After a throat or skin infection with certain streptococci, immune complexes inflame the glomeruli and cause the classic nephritic syndrome.
What it is
Postinfectious glomerulonephritis follows an infection, classically with nephritogenic group A streptococci, by one to several weeks, the time needed to make antibodies. Streptococcal antigens such as SpeB settle in the glomerulus and form complexes that activate complement. Children usually recover; adults do less well. A related form occurs during ongoing infections, notably staphylococcal ones in older or diabetic adults, and can be IgA-dominant.
Structure
- Kidneys are enlarged and pale, sometimes with petechiae on the surface.
- Glomeruli are swollen and bloodless, packed with proliferating endothelial and mesangial cells and neutrophils.
- Electron microscopy shows dome-shaped electron-dense humps on the epithelial side of the basement membrane.
- Interstitial edema and red cell casts in tubules are common.
Step by step
- A nephritogenic streptococcus infects the throat or skin.
- Bacterial antigens, such as the cationic protease SpeB, reach the glomeruli.
- Antibodies made over the next one to two weeks bind them in place or as circulating complexes.
- Complement is consumed (low C3) and neutrophils and monocytes are drawn in.
- Inflamed capillaries close: GFR falls, red cells leak, salt is retained and blood pressure rises.
- In most children the deposits clear and function returns; some adults keep proteinuria or progress.
Clinical notes
- Cola-coloured urine, periorbital edema and hypertension in a child after a sore throat or impetigo.
- Persistent low complement beyond two months suggests another disease (MPGN, C3 glomerulopathy, lupus).
- Infection-associated GN in endocarditis, abscesses or shunt infections clears only when the infection is treated.
Test yourself
Think of the answer, then tap the question to see it.
Why is there a delay between strep throat and glomerulonephritis?
Antibodies must be produced before immune complexes can form in the glomeruli.
What does electron microscopy show in poststreptococcal GN?
Subepithelial humps: dome-shaped electron-dense deposits on the epithelial side of the basement membrane.
What happens to C3 and how long does it last?
C3 falls during the acute phase and usually returns to normal within about eight weeks.
How does staphylococcal infection-associated GN differ?
It occurs during the infection, often in older diabetic adults, and the deposits are frequently IgA-dominant.
Elsewhere in DurgiPedia
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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Poststreptococcal glomerulonephritis (GN): MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2025).
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Representative model, for educational purposes only.