Overview
Also known as crescentic glomerulonephritis, rapidly progressive glomerulonephritis (RPG) is a syndrome describing the following 3 elements:
- At least a 50% decline in kidney function over 3 months:
- This may be quicker over days to weeks
- Nephritic syndrome:
- Haematuria, hypertension, oliguria, proteinuria
- Histopathological findings:
- Crescents are seen on a renal biopsy. These form due to inflammation damaging glomerular capillaries.
RPG is not a singular disease process. It describes the above elements and has multiple underlying causes, which are classified based on histological and immunological findings into:
- Type I RPG – antibody-mediated disease (type II hypersensitivity)
- Type II RPG – immune complex disease (type III hypersensitivity)
- Type III RPG – pauci-immune (no immune complexes present or antibodies directed at glomerular tissue)
In some cases, it can lead to end-stage kidney disease within weeks to months.
Causes
Type I RPG
This is also known as anti-glomerular basement membrane (anti-GBM) disease or Goodpasture’s syndrome, which is characterised by the presence of autoantibodies against type IV collagen in the glomerular basement membrane (GBM).
Type II RPG
This is characterised by immune complexes (made of antigens bound to antibodies) which are deposited in the glomeruli leading to damage and inflammation. This process is also described by type III hypersensitivity. Causes include:
- IgA nephropathy
- Post-streptococcal glomerulonephritis
- Lupus nephritis
Type III RPG
This is characterised by RPG without anti-GBM antibodies or immune complexes present. Around 80-90% of cases are positive for anti-neutrophil cytoplasmic antibodies (ANCA). Causes tend to include small-vessel vasculitides such as:
- Granulomatosis with polyangiitis (Wegener’s granulomatosis)
- Eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome)
- Microscopic polyangiitis
