Positive Antineutrophil Cytoplasmic Antibody Serology in Patients with Lupus Nephritis is Associated with Distinct Histopathologic Features on Renal Biopsy.

Class IV-S lupus nephritis is often associated with more necrosis and fewer subendothelial immune deposits compared to class IV-G lupus nephritis, suggestive of necrotising glomerular inflammation found in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis. ANCAs are present in a significant proportion of patients with lupus nephritis. Here we determine whether ANCAs are associated with distinct clinical and histopathologic features of lupus nephritis. Thirty-two ANCA-positive biopsies were compared to 222 ANCA-negative biopsies from patients with lupus nephritis. The majority (82%) of ANCA-positive patients had antimyeloperoxidase antibodies. Class IV-S lupus nephritis and glomerular necrosis were significantly more common (36% vs. 16% and 35% vs. 15%, respectively) and isolated Class V lupus nephritis significantly less common (10% vs. 29%) in the ANCA-positive group. ANCA-positive patients had significantly higher dsDNA titers (335u/ml vs. 52u/ml), significantly lower serum C4 concentrations (0.125g/L vs. 0.15g/L) and significantly higher serum creatinine (130μmol/L vs. 84μmol/L) at the time of biopsy. Hence ANCAs appear to influence the histological pattern of lupus nephritis and are associated with worse baseline renal function and more active lupus serology. There was no significant difference in outcome between groups when matched for severity of disease and treatment using propensity scoring. Thus, further studies are needed to examine whether ANCAs in patients with lupus nephritis have a pathogenic role and whether they are associated with worse renal outcomes or are simply a marker of more severe disease.