Renal vascular lesions in childhood-onset lupus nephritis.

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 kidney outcome was defined as advanced chronic kidney disease (CKD) stage 3-5, kidney failure 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 ± 39.4 ml/min/1.73m², p = 0.005), haemoglobin level (9.1 ± 1.9 vs. 10.4 ± 1.9 g/dL, p = 0.008) and platelet count (150.1 ± 96.4 vs. 217.2 ± 104.8 × 10⁹/L, p = 0.01). LN classes and activity/chronicity indices were similar. Patients with RVLs had poorer composite kidney outcomes, though not reaching statistical significance (log-rank test, p = 0.06). The presence of NNV was associated with inferior survival free from composite kidney 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 kidney outcome.

Conclusion: RVLs are present in one-fifth of cLN patients and are associated with severe presentation. NNV is associated with worse long-term kidney outcome. Routine evaluation of RVLs is warranted and should be incorporated into future classification criteria.