Characteristics and renal survival of patients with lupus nephritis with glomerular immunoglobulin G4 deposition: a single-centre retrospective analysis.

OBJECTIVE:Renal injury is common in SLE. Immune complex deposition plays an important role in the development of lupus nephritis (LN), while little is known about glomerular IgG4 deposition in patients with LN. This study aimed to investigate the characteristics and renal outcome of patients with LN with glomerular IgG4 deposition. METHODS:This is a single-centre retrospective study enrolling 89 patients with biopsy-proven LN. Clinicopathological features, treatment responses and renal outcomes were collected and compared between patients with and without glomerular IgG4 deposition. Renal outcome events include progression of renal dysfunction and end-stage renal disease. RESULTS:Thirty (33.7%) patients had glomerular IgG4 deposition. Patients with glomerular IgG4 deposition had lower serum albumin level (25.06±8.61 g/L vs 28.29±6.31 g/L, p=0.05), more class V LN (60.0% vs 35.6%, p=0.03), more positive phospholipase A2 receptor (PLA2R) staining (43.3% vs 18.6%, p=0.01), more IgG1 deposits (96.7% vs 64.4%, p=0.01) and less C3 deposits (46.7% vs 72.9%, p=0.02) than those without glomerular IgG4 deposition. They also had better renal survival than those without glomerular IgG4 deposition (96.7% vs 79.7%, p=0.03). Multivariate Cox regression showed that high serum creatinine level (relative risk (RR)=1.005, 95% CI 1.002 to 1.008, p=0.01) and high Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) scores (RR=1.078, 95% CI 1.004 to 1.157, p=0.04) independently correlated with poor renal outcome, while glomerular IgG4 deposition tended to correlate with good renal outcome (RR=5.95, 95% CI 0.759 to 45.97, p=0.09). Further, patients with both glomerular IgG4 and PLA2R positivity (n=13) had higher levels of serum C3 and C4 and less glomerular C3 deposits compared with those with positive IgG4 but negative PLA2R in the glomerulus (n=17), and had a tendency of low SLEDAI score (p=0.07). CONCLUSIONS:Patients with LN with glomerular IgG4 deposits may have better renal survival, and patients with LN with simultaneous glomerular IgG4 and PLA2R deposits may have low disease activity.