Abstract: FR-PO0819
Exostosin 1 (EXT1) Expression in Lupus Membranous Nephropathy: Prevalence, Clinicopathological Correlations, and Kidney Outcomes
Session Information
- Glomerular Diseases: Practice and New Concepts Shaping Modern Care
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
- Assis, Luiza Liza de, Universidade de Sao Paulo Faculdade de Medicina, São Paulo, SP, Brazil
- Malheiros, Denise M., Universidade de Sao Paulo Faculdade de Medicina, São Paulo, SP, Brazil
- Zanetta, Dirce M T, Universidade de Sao Paulo, São Paulo, SP, Brazil
- Yu, Luis, Universidade de Sao Paulo Faculdade de Medicina, São Paulo, SP, Brazil
Background
Lupus nephritis (LN) is a severe complication of systemic lupus erythematosus (SLE) associated with significant morbidity and mortality. The EXT1/EXT2 heterodimer has emerged as a novel antigen in lupus membranous nephropathy (LMN), with undefined clinicopathological and prognostic significance.
Methods
Retrospective cohort study including 97 LMN patients (ISN/RPS class V or III/IV+V) and 14 controls at Hospital das Clinicas, University of Sao Paulo, Brazil (2014–2022). Immunohistochemistry for EXT1 was performed on all biopsies. Groups were compared using descriptive analyses and repeated measures models over a median follow-up of 48 months.
Results
EXT1 positivity was identified in 35.1% (34/97), more frequent in pure LMN (40%) than with a proliferative component (32%). No controls tested positive. The cohort was predominantly female (86.6%), median age 35 years; 67% had a proliferative component. EXT1-positive patients had a higher frequency of antiphospholipid antibodies (40% vs. 15.4%; p=0.035), with no correlation with thrombotic microangiopathy. Notably, 33.7% had initiated induction therapy and 38.0% were on maintenance immunosuppression at biopsy. No significant differences were observed in creatinine, eGFR, proteinuria, or histological indices at presentation. Despite similar baseline profiles, EXT1-negative patients more frequently received cyclophosphamide (57.6% vs. 34.5%; p=0.041), while EXT1-positive patients received mycophenolate (44.8% vs. 22.0%; p=0.027). At one year, EXT1-positive patients showed greater C3 (30.8% vs. 12.1%; p=0.038) and C4 (30.8% vs. 10.3%; p=0.020) consumption, though not sustained. No differences were observed in treatment response rates, primary composite endpoint (eGFR decline ≥40% or ESKD), or mortality.
Conclusion
EXT1 prevalence was consistent with the literature, reinforcing its epidemiological reproducibility across diverse populations. The higher frequency of antiphospholipid antibodies in EXT1-positive patients warrants further investigation. Given the limited sample size and prior immunosuppressive therapy, findings should be interpreted with caution.
Funding
- Government Support – Non-U.S.