Antineutrophil cytoplasmic autoantibody-negative pauci-immune crescentic glomerulonephritis

Pauci-immune crescentic glomerulonephritis (CrGN) is one of the most common causes of rapidly progressive glomerulonephritis. The majority of patients with pauci-immune CrGN had circulating antineutrophil cytoplasmic autoantibody (ANCA). However, patients with ANCA-negative pauci-immune CrGN were not investigated fully. This study aimed to analyze the characteristics of this subgroup of patients. Patients whose pauci-immune CrGN was diagnosed from 1997 to 2006 in one center were studied retrospectively. The criteria of pauci-immune was defined as "the intensity of glomerular immunoglobulins staining by direct immunofluorescence assay in renal sections was negative to 1+ staining on a scale of 0 to 4+." Clinical and pathologic characteristics were compared between patients with and without ANCA. Among the 85 patients with pauci-immune CrGN, 28 (32.9%) were ANCA negative. Compared with the 57 ANCA-positive patients, the ANCA-negative patients were much younger (39.7 +/- 17.0 versus 57.6 +/- 14.0 yr; P < 0.001). The level of urinary protein and the prevalence of nephrotic syndrome were significantly higher in ANCA-negative patients than that in ANCA-positive patients (P < 0.01 and P < 0.001, respectively). However, the prevalence of extrarenal involvement was significantly lower in ANCA-negative patients than that in ANCA-positive patients. The renal survival was poorer in ANCA-negative patients than that in ANCA-positive ones (P < 0.05). ANCA-negative pauci-immune CrGN was not rare and might represent an independent disease entity from ANCA-positive vasculitis.