Abstract: SA-PO763
ANCA and Anti-glomerular Basement Membrane (GBM) Dual Antibody Positivity: A Case Series and Proposal for a Clinical Classification
Session Information
- ANCA-Associated Vasculitis, Anti-GBM Disease, and Other RPGN
October 26, 2024 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Glomerular Diseases
- 1402 Glomerular Diseases: Clinical, Outcomes, and Therapeutics
Authors
- O'Sullivan, Tara, Cork University Hospital, Cork, Cork, Ireland
- Clarkson, Michael, Cork University Hospital, Cork, Cork, Ireland
- Conlon, Niall P., St James's Hospital, Dublin, Ireland
- Griffin, Matthew D., Galway University Hospitals, Galway, Galway, Ireland
- Mc Monagle, Edward Philip, University Hospital Limerick, Dooradoyle, Limerick, Ireland
- Little, Mark Alan, The University of Dublin Trinity College, Dublin, Ireland
- Moran, Sarah Margaret, Cork University Hospital, Cork, Cork, Ireland
Background
Anti-glomerular basement membrane (aGBM) disease and the anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAV) are rare vasculitides. ANCA and aGBM dual positivity can occur; up to 40% of patients with a clinical diagnosis of aGBM disease have a positive ANCA (aGBM+AAV) and up to 5% of patients with a clinical diagnosis of AAV have detectable aGBM antibodies (AAV+aGBM). Literature on clinical phenotyping and prognosis is lacking, with no current clinical consensus on definitions.
We report a case series of aGBM+AAV and AAV+aGBM from RITA-Ireland, with the following proposed definitions:
1. aGBM+AAV: aGBM disease with linear IgG staining on kidney biopsy and no clinical features of vasculitis outside lung or kidney, with co-existent ANCA positivity in serum
2. AAV+aGBM: clinical AAV with aGBM antibody (pauci immune kidney biopsy findings)
Methods
Dual positive patients with documented renal biopsy were identified from the European reference Network RITA-Ireland Vasculitis (RIV) Registry and Biobank. Clinical and biochemical features, aGBM methodology, renal biopsies, requirement for RRT, progression to ESKD, recovery of renal function, treatment, relapse, and death were retrospectively compared between the two groups.
Results
Thirty patients meeting the inclusion criteria were identified, 7 (23.3%) with AAV+aGBM and 23 (76.7%) with aGBM+AAV. Anti-myeloperoxidase (MPO) antibody was detected in 70%. See figure 1 for results and comparison between groups.
Conclusion
AAV and aGBM disease are rare vasculitides, whose overlap occurs at a higher frequency than determined by chance. There is currently no consensus on nomenclature of aGBM+AAV and AAV+aGBM. This case series highlights differences between these diseases, most notably the higher proportion of relapse in aGBM+AAV, and informs a proposal for a clinical classification to guide future care pathways.