Abstract: FR-PO0641
Primary Anti-C1q-Associated Renal Vasculitis: A Clinicopathologic Case Series
Session Information
- Glomerular Diseases: Clinical, Outcomes, and Therapeutics Research - ANCA/FSGS
October 23, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Glomerular Diseases
- 1402 Glomerular Diseases: Clinical, Outcomes, and Therapeutics
Authors
- Stefan, Teodor, Institutul Clinic Fundeni, Bucharest, Romania
- Lujinschi, Stefan Nicolaie, Institutul Clinic Fundeni, Bucharest, Romania
- Ismail, Gener, Institutul Clinic Fundeni, Bucharest, Romania
Background
Anti-C1q antibodies are classically associated with lupus nephritis and hypocomplementemic urticarial vasculitis, but their role in primary small vessel vasculitis and asscociated renal lesions remains poorly characterized. We describe the clinicopathologic spectrum and longitudinal outcomes of 4 patients with primary anti-C1q-associated renal vasculitis without systemic lupus erythematosus (SLE).
Methods
We retrospectively analyzed 4 patients with positive anti-C1q antibodies and clinicopathologic features suggestive of small vessel vasculitis with renal involvment. Patients with SLE or other autoimmune diseases were excluded. Clinical, immunologic, histopathologic, treatment, and outcome data were collected.
Results
Patients were aged 24-61 years. Three were male. Follow-up ranged from 8 to 91 months. Clinical presentations included: rapidly progressive glomerulonephritis (n=1), nephritic-nephrotic syndrome (n=1), nephrotic syndrome (n=1), and subnephrotic proteinuria (n=1). Three patients exhibited cutaneous vasculitic manifestations and 3/4 had hypocomplementemia. ANA, anti-dsDNA, ANCA, and cryoglobulins were negative in all cases. Kidney biopsy (n=3) showed heterogeneous patterns including membranoproliferative glomerulonephritis (n=1), C1q-dominant immune-complex mediated glomerulonephritis (n=1) and focal segmental glomerulosclerosis with mesangial C1q deposits (n=1). Active lesions included: endocapillary proliferation (n=2), crescents (n=2) and fibrinoid necrosis (n=2). Induction therapy included: rituximab (n=2), rituximab plus cyclophosphamide (n=1) and cyclophosphamide alone (n=1). At last follow-up, 3 patients achieved complete renal response and one achieved partial renal response. No patient required kidney replacement therapy. Complement abnormalities improved (n=1) or normalized (n=3) in all patients. No patient achieved immunological remission. Only one patient experienced renal relapse 23 months after remission, requiring retreatment.
Conclusion
Primary anti-C1q-associated renal vasculitis may represent an underrecognized complement-mediated clinicopathologic spectrum characterized by severe renal involvement, heterogeneous renal pathology, and persistent anti-C1q positivity despite clinical response.