Classification of primary RPGN
How is primary RPGN classified?
RPGN can occur as a primary disorder in the absence of other glomerular or systemic diseases.
Crescentic nephritis, the pathologic correlate of RPGN, is classified into three types using immunofluorescence microscopy to describe the presence or absence of immune deposits and the character of their distribution within the glomerular basement membrane:
1. Type I RPGN is characterized by linear deposition of antibodies directed against type IV collagen, a matrix protein that is a constituent of the GBM. These antibodies are commonly referred to as anti-GBM antibodies (discussed later). Type I RPGN comprises approximately 10% to 20% of patients with primary RPGN without pulmonary hemorrhage.
2. Type II RPGN is characterized by a granular pattern of immune complex deposition. This is found in 20% to 30% of patients with primary RPGN without pulmonary hemorrhage.
3. Type III RPGN has no immune deposits (“pauci-immune”) in glomeruli using immunofluorescence or electron microscopy, and occurs in 50% to 60% of patients with crescentic glomerulonephritis on kidney biopsy.
Classification of RPGN
Type I: Anti-GBM antibody disease (Goodpasture disease)
Type II: Granular glomerular immune complex association
Type III: Pauci-immune glomerulonephritis
Secondary to systemic disease
Superimposed on a primary glomerular disease
Post-streptococcal and rarely post-viral glomerulonephritis
Visceral abscess and other infection-associated
- Small Vessel (Pauci-Immune):
- Microscopic polyangiitis
- Granulomatosis with polyangiitis (Wegener’s syndrome)
- Eosinophilic granulomatosis (Churg-Strauss syndrome)
- Small Vessel (Immune Complex):
- Systemic lupus erythematosus
- Henoch-Schönlein purpura
- Medium Vessel:
- Polyarteritis nodosa (rare)
- Goodpasture syndrome and disease
- ANCA-associated (hydralazine, propylthiouracil, minocycline)
- Drug-induce lupus
ANCA , Anti-neutrophil cytoplasmic antibodies; GBM , glomerular basement membrane; RPGN , rapidly progressive glomerulonephritis.