Nephritic syndrome

	PSGN	IgA Nephropathy	Alport Syndrome	RPGN (Crescentic)	DPGN (Lupus)	MPGN
Classic Patient	Child, 2-4 wks post-GAS infx	Young adult, syn-pharyngitic	Boy w/ fam hx of renal failure & deafness	Pt w/ acute, rapid GFR decline	Patient with SLE	Assoc. w/ HCV, cancer, or autoimmune dz
Pathophysiology	Type III HSR; IC deposition	Mesangial IgA IC deposition	X-linked defect in Type IV Collagen	GBM breaks → fibrin influx	Type III HSR; diffuse IC deposition	IC deposition or complement dysregulation
Key Features / Labs	↓↓ C3, ↑ASO titer	Normal C3, episodic gross hematuria	Hematuria, sensorineural deafness, ocular defects	Anti-GBM Ab, p/c-ANCA depending on type	↓↓ C3/C4, +anti-dsDNA	↓↓ C3 (persistent), +HCV serology
LM/IF/EM	Subepithelial humps (EM), hypercellular “lumpy bumpy” (LM), granular IgG/C3 (IF)	Mesangial IgA deposits (IF)	“Basket-weave” GBM (EM)	Crescents (LM); IF defines type (linear, pauci, granular)	“Wire loops” (LM), subendothelial deposits (EM), “full-house” (IF)	“Tram-track” GBM (LM)
Key Fact	Prognosis excellent in children	Most common GN worldwide.	”Can’t see, can’t pee, can’t hear a high C”	A histologic pattern, not a single disease.	Most common & severe nephritis in SLE.	Strong association with Hepatitis C (Type I).

Etiology

Tip

• The most common cause of nephritic syndrome is immune complex deposition, which leads to serum hypocomplementemia.
• IgA nephropathy is an exception, which is characterized by normal serum complement levels

• ANCA-associated glomerulonephritis (pauci-immune glomerulonephritis)
  • Granulomatosis with polyangiitis
  • Microscopic polyangiitis
  • Eosinophilic granulomatosis with polyangiitis
• Anti-glomerular basement membrane (GBM) associated glomerulonephritis
  • Anti-GBM disease (Goodpasture disease)
  • Anti-GBM glomerulonephritis (no lung involvement)
• Immune complex-mediated glomerulonephritis
  • Low C3 levels
    • Lupus nephritis
    • Infection-related glomerulonephritis
      • Poststreptococcal glomerulonephritis
  • Normal C3 levels
    • IgA nephropathy
    • IgA vasculitis

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Classifications

• Poststreptococcal glomerulonephritis
• Diffuse proliferative glomerulonephritis
• Rapidly progressive glomerulonephritis

Pathophysiology

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Clinical features

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Diagnostics

• Initial: Urinalysis (UA) showing microscopic/macroscopic hematuria, dysmorphic RBCs, RBC casts, and sub-nephrotic range proteinuria (< 3.5 g/day).
• Key Labs:
  • Renal function: Elevated BUN and serum Cr.
  • Serum complements:
    • Decreased C3/C4: PSGN, Lupus Nephritis, Membranoproliferative GN (MPGN).
    • Normal C3/C4: IgA Nephropathy, Granulomatosis with Polyangiitis (GPA), Microscopic Polyangiitis (MPA), Goodpasture syndrome.
  • Serology: Anti-streptolysin O (ASO) or anti-DNase B (PSGN); ANA and anti-dsDNA (SLE); c-ANCA/PR3 (GPA); p-ANCA/MPO (MPA); anti-GBM antibodies (Goodpasture).
• Confirmatory/Gold Standard: Renal biopsy (not always needed in classic pediatric PSGN, but required in adults or progressive cases).
  • PSGN: LM shows diffuse hypercellularity; IF shows granular deposition (“lumpy-bumpy” C3/IgG); EM shows subepithelial humps.
  • IgA Nephropathy: IF shows IgA-dominant immune complex deposition in the mesangium.
  • Goodpasture Syndrome: IF shows linear IgG deposition along the GBM.
  • RPGN: LM shows crescents composed of fibrin and macrophages.
  • Pauci-immune GN (GPA/MPA): Biopsy shows necrotizing GN with minimal or absent immune complexes on IF.

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Treatment

General / Supportive

• Primary Goal: Control volume overload & HTN.
• Methods: Salt/fluid restriction, Loop Diuretics (Furosemide), and ACEi/ARBs (especially with proteinuria).

Disease-Specific Tx

• Post-streptococcal GN (PSGN):
  • Supportive care only. Antibiotics treat the strep infection but do not alter the course of the GN.
• IgA Nephropathy (Berger’s):
  • ACEi/ARBs are first-line. Add corticosteroids if proteinuria persists (>1g/day) and GFR is preserved.
• Lupus Nephritis (Class III/IV):
  • Induction: Corticosteroids + Mycophenolate (MMF) or Cyclophosphamide.
  • Maintenance: MMF or Azathioprine.
• ANCA-Associated Vasculitis (e.g., GPA/MPA):
  • Induction: Corticosteroids + Rituximab or Cyclophosphamide.
• Anti-GBM Disease (Goodpasture’s):
  • Emergency Tx: Plasmapheresis + Corticosteroids + Cyclophosphamide.

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