Overview
Definition
An immune complex-mediated glomerulonephritis that occurs weeks after infection with certain nephritogenic strains of Group A beta-hemolytic Streptococcus.
Epidemiology
Most commonly affects children aged 5-12 years. Usually resolves spontaneously.
Etiology & Risk Factors
- Preceding infection with Group A Strep (Streptococcus pyogenes) - either Pharyngitis (1-2 weeks prior) or Impetigo (3-6 weeks prior)
- Immune complexes (IgG, IgM, and C3) deposit in the glomerular basement membrane (Type III Hypersensitivity).
Clinical Symptoms
- Classic Nephritic Triad: Hematuria, Hypertension, and Edema (especially periorbital)
- Oliguria (decreased urine output)
- Gross hematuria ('Cola-colored' or 'Tea-colored' urine)
Clinical Approach
Diagnosis
- Urine Microscopy: RBC casts and dysmorphic RBCs (hallmarks of glomerular bleeding), mild proteinuria (< 3.5g/day)
- Blood tests: Low C3 complement levels (consumed by immune complexes), elevated ASO titer or Anti-DNAse B antibodies
- Renal Biopsy (rarely needed): 'Lumpy-bumpy' immunofluorescence pattern, Subepithelial 'humps' on electron microscopy
Management
- Supportive care is the mainstay
- Loop diuretics for volume overload and edema
- Anti-hypertensives (CCBs or ACE inhibitors) for blood pressure control
- Antibiotics ONLY if the active streptococcal infection is still present (does not alter the course of the glomerulonephritis)
Complications
- Acute Kidney Injury (AKI) requiring transient dialysis
- Hypertensive encephalopathy (due to rapid fluid retention)
- Progression to chronic kidney disease (very rare in children, slightly higher risk in adults)