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Rapidly progressive glomerulonephritis

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Rapidly Progressive Glomerulonephritis (RPGN)

Definition

RPGN is a clinicopathologic syndrome, not a single disease, defined by rapid loss of kidney function (over days to weeks) occurring in the setting of nephritic syndrome - glomerular hematuria (dysmorphic RBCs, RBC casts), hypertension, edema, and non-nephrotic-range proteinuria. Untreated, it progresses to end-stage kidney disease (ESKD) - hence the urgency of diagnosis (National Kidneys Foundation Primer on Kidney Diseases, 8e; Comprehensive Clinical Nephrology, 7th Edition, p. 556).
The histologic correlate is crescentic glomerulonephritis - proliferation of cells (parietal epithelial cells plus infiltrating monocytes/leukocytes) within Bowman's space, forming a "crescent" shape on cross-section, usually accompanied by segmental capillary necrosis and fibrin deposition (Robbins & Kumar Basic Pathology, p. 2323).

Classification - Three Immunopathologic Types

1. Anti-GBM antibody-mediated (Type I)
  • Linear deposits of IgG (and often C3) along the glomerular basement membrane on immunofluorescence (type II hypersensitivity).
  • When anti-GBM antibodies cross-react with pulmonary alveolar basement membrane, causing pulmonary hemorrhage plus renal failure, this is Goodpasture syndrome.
2. Immune complex-mediated (Type II)
  • Granular ("lumpy-bumpy") staining for immunoglobulin/complement on immunofluorescence.
  • Complicates postinfectious GN, SLE (lupus nephritis), IgA nephropathy, Henoch-Schonlein purpura/IgA vasculitis, and other immune-complex nephritides; often shows endocapillary proliferation in addition to crescents.
3. Pauci-immune (Type III)
  • Little or no immunoglobulin/complement deposition on immunofluorescence.
  • Most are associated with circulating ANCA (PR3-ANCA or MPO-ANCA), reflecting an underlying systemic vasculitis (granulomatosis with polyangiitis, microscopic polyangiitis, eosinophilic granulomatosis with polyangiitis); a subset is renal-limited/idiopathic.
Light microscopy is essentially indistinguishable between anti-GBM and ANCA-associated pauci-immune crescentic GN - immunofluorescence and serology are what separate the categories (Brenner and Rector's The Kidney, 2-Vol Set).

Clinical Presentation

  • Nephritic sediment (dysmorphic RBCs, RBC casts) with rapidly rising creatinine, oliguria/anuria in severe cases.
  • May present as a uremic emergency, or during workup of a systemic illness (vasculitis, lupus, infection).
  • Pulmonary-renal syndrome: concomitant pulmonary hemorrhage occurs with both ANCA-associated pauci-immune GN and anti-GBM disease (Goodpasture syndrome).

Diagnostic Workup

  • Serologies: ANCA (PR3/MPO), anti-GBM antibody, ANA/anti-dsDNA and complement levels (C3/C4), antistreptolysin/streptozyme, blood cultures (endocarditis), cryoglobulins, serum IgA.
  • Renal biopsy is essential - confirms crescent formation, determines the immunofluorescence pattern (linear vs. granular vs. pauci-immune), and grades chronicity (percentage of crescents, degree of fibrosis) which guides prognosis and treatment intensity.

Treatment

Because RPGN causes irreversible glomerular/renal destruction within days to weeks, treatment must start urgently, often before biopsy results are finalized, based on the leading clinical suspicion.
  • Corticosteroids (pulse IV methylprednisolone followed by oral taper) - cornerstone of induction therapy across all three subtypes.
  • Cyclophosphamide - added for ANCA-associated and anti-GBM disease; rituximab is an accepted alternative/addition in ANCA-associated vasculitis.
  • Plasma exchange (plasmapheresis) - established for anti-GBM disease (removes circulating pathogenic antibody), particularly when there is severe renal impairment, dialysis dependence, or pulmonary hemorrhage; data in Brenner and Rector's show renal recovery is far better in patients with lower initial creatinine when treated early with plasma exchange plus immunosuppression, and outcomes are poor once creatinine is very high or dialysis-dependent - underscoring that early diagnosis and treatment before advanced fibrosis/crescent formation is the single biggest determinant of renal recovery.
  • Underlying cause-specific therapy (e.g., antibiotics for postinfectious/endocarditis-associated GN, treatment of SLE) as appropriate.

Prognosis

Prognosis correlates with the percentage of glomeruli with crescents at biopsy, degree of interstitial fibrosis, and creatinine at presentation. Anti-GBM disease tends to be the most aggressive; delayed treatment (especially once dialysis-dependent) is associated with a low chance of renal recovery.
Recent systematic-review literature (PMID: 36835388, 2023) supports adjunctive plasma exchange specifically in rapidly progressive IgA nephropathy/Henoch-Schonlein purpura nephritis, consistent with the library's emphasis on early, aggressive combined therapy. No major evidence has emerged in the last 2-3 years that contradicts the classic three-category classification or standard steroid/cyclophosphamide-or-rituximab plus plasma exchange approach summarized above.
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