#2555 C4d—a novel predictor of the disease progression and treatment failure in primary focal segmental glomerulosclerosis?

Abstract

Abstract Background and Aims Complement system seems to play a role in the pathogenesis of primary focal segmental glomerulosclerosis (pFSGS) where, due to unpredictable clinical course and outcome, novel prognostic factors are sought. The split product of C4 and tissue marker of complement activation, C4d, is a potential candidate whose prognostic significance was determined in this study. Method Patients >18 years with features consistent with pFSGS (full blown nephrotic syndrome, diffuse podocyte foot processes effacement and exclusion of known causes of FSGS), were recruited from our Hospital registry of kidney biopsies, from 2003 to 2021. Patients with end-stage renal disease (ESRD) defined as eGFR <15 ml/min/1.73 m2 were not included. Every renal biopsy specimen was analyzed by light, immunofluorescence and electron microscopy with additional immunochemistry for C4d performed on paraffin-embedded tissue using monoclonal rabbit antibody (detection system Ventana BenchMark Ultra). Samples with at least one non-globally sclerosed glomerulus (GSG) were examined by two renal pathologists who classified every non-GSG into C4d positive and negative. Based on ratio of C4d+ non-GGS/total N of non-GSG and C4d+ nonsclerotic glomeruli (NSG)/total N of NSG, patients were stratified into two groups: <50% and ≥50%. Primary outcome was defined as composite of ESRD and initial eGFR declining >50%. Failure to meet criteria for at least partial remission at the last follow-up visit according to KDIGO 2021 Guidelines was defined as treatment failure. Numeric variables are shown as median with interquartile range (IQR) and P value <0.05 was considered as significant. Results Relevant data of 58 included patients with renal outcomes are shown in Table. Median follow up was 90.7 (IQR 48-167) months. Patients with ≥50% of C4d+ non-GSG had higher proportion of treatment failure (Table) and worse renal survival (log-rank test, p = 0.006). In multivariate Cox regression analysis, after inclusion of age, sex, initial eGFR and 24-h proteinuria, IFTA, serum albumin and C4d category, only C4d ≥50% (HR = 4.077, 95% CI 1.101-15.09, p = 0.035) and IFTA (HR = 1.052, 95% CI 1.019-1.085, p = 0.002) remained independent predictors of progression to defined endpoint. Likewise, patients with ≥50% of C4d+ NSG/total N of NSG had higher proportion of treatment failure (chi-square, p = 0.03) and worse renal survival (log-rank, p = 0.037). Conclusion C4d deposition is an independent predictor of disease progression, treatment failure and renal survival in pFSGS. Significant influence of NSG-C4d deposition on disease progression may indicate pathophysiological role of the complement system activation in pFSGS independently of the presence of glomerular sclerosis.