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Does truly 'idiopathic' crescentic glomerulonephritis exist?
R Angangco1, S Thiru, V L Esnault
1Department of Medicine, University of Cambridge School of Clinical Medicine, Addenbrooke's Hospital, UK.
Insights
Truly idiopathic crescentic glomerulonephritis is rare. Most cases previously labeled as such are now identified as anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis, impacting diagnosis and treatment.
Area of Science:
- Nephrology
- Immunology
- Pathology
Background:
- Crescentic glomerulonephritis (CGN) classification includes anti-GBM disease, immune-complex disease, and pauci-immune CGN.
- Pauci-immune CGN encompasses systemic vasculitis and 'idiopathic' isolated CGN.
- Anti-neutrophil cytoplasmic antibodies (ANCA) link many 'idiopathic' cases to renal-limited vasculitis.
Purpose of the Study:
- To determine the prevalence of truly 'idiopathic' crescentic nephritis.
- To re-evaluate the classification of CGN in light of ANCA testing.
Main Methods:
- Retrospective review of renal biopsies with extracapillary proliferation over a 4-year period.
- Analysis of 82 biopsies with sufficient detail for classification.
- Categorization based on anti-GBM disease, epithelial proliferation, and ANCA-associated disease.
Main Results:
- Out of 82 analyzed biopsies, 10 had anti-GBM disease, 35 had epithelial proliferation, and 36 had ANCA-associated disease.
- Nine ANCA-associated cases lacked extrarenal features, previously misclassified as 'idiopathic'.
- Only one patient had inactive glomerulonephritis with interstitial nephritis, not fitting typical CGN.
Conclusions:
- Truly 'idiopathic' crescentic glomerulonephritis is exceedingly rare, if it exists.
- ANCA testing significantly improves CGN classification, distinguishing renal-limited vasculitis.
- Accurate classification has critical implications for patient prognosis and therapeutic strategies.
Abstract:
Crescentic glomerulonephritis is usually classified into antiglomerular basement membrane (GBM) disease, immune-complex disease, or pauci-immune crescentic nephritis. The last category includes patients with systemic vasculitis as well as 'idiopathic' isolated crescentic nephritis. The presence of anti-neutrophil cytoplasmic antibodies (ANCA) in many patients with apparently isolated crescentic nephritis suggests that this represents a renal-limited form of vasculitis, and that truly 'idiopathic' crescentic nephritis is a very rare entity. We reviewed all renal biopsies with extracapillary proliferation seen at our centre since the availability of an ANCA assay (4-year period). There were 89 such biopsies of a total of 1240, of which 82 had sufficient details for further analysis. Of these, 10 had anti-GBM disease, 35 had epithelial proliferation associated with a variety of other diseases, and 36 had ANCA-associated disease. Nine of this last group had no extrarenal features and would previously have been classified as 'idiopathic' crescentic glomerulonephritis. The single remaining patient had an inactive glomerulonephritis with a scarred crescent; the predominant lesion was an interstitial nephritis. We therefore conclude that truly 'idiopathic' crescentic nephritis is very rare, if it exists at all. The ability to provide a practically complete classification of crescentic nephritis has important prognostic and therapeutic consequences.