Renal vascular lesions in Childhood-onset Lupus Nephritis

Abstract Background: This study aimed to determine the clinical significance of renal vascular lesions (RVLs) in childhood-onset lupus nephritis (cLN). Methods: We retrospectively reviewed all children with biopsy-proven cLN between 2004-2020 to evaluate the prevalence of RVLs on kidney biopsy and its associated factors and long-term outcomes. The composite renal outcome was defined as advanced chronic kidney disease (CKD) stage 3-5, end-stage kidney disease (ESKD) and death. Results: 107 biopsies from 84 Chinese patients were analysed. RVLs were observed in 19 patients (22.6%), including non-inflammatory necrotizing vasculopathy (NNV, n=6), thrombotic microangiopathy (TMA, n=4), arterial sclerosis (AS, n=3), concurrent NNV with AS (n=4), concurrent NNV with TMA (n=1) and concurrent true renal vasculitis with AS (n=1). The presence of RVLs was associated with lower estimated glomerular filtration rate (eGFR) (66.9±40.3 vs 95.6±39.4ml/min/1.73m², p=0.005), haemoglobin level (9.1±1.9 vs 10.4±1.9g/dL, p=0.008) and platelet count (150.1±96.4 vs 217.2±104.8 x 10⁹/L, p=0.01). LN classes and activity/chronicity indices were similar. Patients with RVLs had poorer composite renal outcomes, though not reaching statistical significance (log-rank test, p=0.06). The presence of NNV was associated with inferior survival free from composite renal outcome (log-rank test, p = 0.0018), compared to other forms of RVLs and those without RVLs. Univariate analysis revealed NNV (HR 7.08, 95% CI 1.67-30.03) was predictive of composite renal outcome. Conclusion: RVLs are present in one-fifth of cLN patients and are associated with severe presentation. NNV is associated with worse long-term renal outcome. Routine evaluation of RVLs is warranted and should be incorporated into future classification criteria.