Antineutrophil cytoplasmic antibody negative pauci-immune extracapillary glomerulonephritis

Pauci-immune extracapillary glomerulonephritis (PEGN) is one of the most common causes of rapidly progressive glomerulonephritis and is usually associated with circulating anti-neutrophil cytoplasmic antibodies (ANCAs). However, a significant number of individuals with PEGN test negative for ANCA and this study aimed to analyze the characteristics of this subgroup of patients.

Patients from two centres who were diagnosed with PEGN between 1997 and 2014 were studied retrospectively. Clinicopathological characteristics and renal outcome were compared between patients presenting with pauci-immune necrotizing extracapillary glomerulonephritis associated or not with the presence of circulating ANCA.

Among the 114 patients with PEGN, 29 (25.4%) were ANCA negative. Compared with the 85 ANCA-positive patients, ANCA-negative patients were younger at the onset (54.8 ± 17.2 vs. 62 ± 14.0 years; P < 0.05). The median level of urinary protein excretion was significantly higher among ANCA-negative patients (3.1 vs. 1 g/24 h; P < 0.001), whereas no differences were found in renal function and need for dialysis between ANCA-negative and positive groups. Extrarenal involvement was present independently of ANCA status. Histological analysis showed that ANCA-negative patients were more likely to have mesangial proliferation (P < 0.05). Renal and global survival were similar between ANCA-negative and positive patients, and treatment response and relapse rates were comparable in both groups.

ANCA-negative pauci-immune extracapillary glomerulonephritis is not a rare condition and is part of a systemic vasculitis disease. Although ANCA-negative patients have renal and histological characteristics that differ from ANCA-positive patients, renal survival and treatment response in PEGN are independent of ANCA status.