BACKGROUND: Several authors have reported cases of anti-neutrophil cytoplasmic antibody (ANCA)-associated crescentic glomerulonephritis (CGN) with definite immune complex (IC) deposits, however, the clinical and pathological significance of IC deposits in patients with ANCA-associated CGN remains unclear. METHODS: Renal biopsy specimens from 28 patients with a diagnosis of CGN and positivity for anti-myeloperoxidase (MPO)-ANCA were retrospectively evaluated. Clinical data were compared between patients with IC deposits (Group A) and patients without IC deposits (Group B). RESULTS: In 12 patients (43%; Group A), IC deposits were detected in the mesangium and/or along the glomerular capillary walls, while typical pauci-immune CGN without IC deposits was found in 16 patients (57%; Group B). Compared with Group B, Group A had lower levels of MPO-ANCA (171 ± 156 vs. 352 ± 299 EU) and C-reactive protein (CRP) (0.63 ± 1.04 vs. 4.45 ± 4.00 mg/dl), as well as less pulmonary involvement (8.3% vs. 56.3%) at diagnosis. However, Group A had significantly heavier proteinuria (2.46 ± 1.67 vs. 0.76 ± 0.52 g/d). Group A was classified into three subgroups: Group A1 with mesangial IgA and C3 deposits, A2 with mesangial IgG and C3 deposits, and A3 with IgG and C3 deposits mainly in the capillary walls. CONCLUSIONS: ANCA-associated CGN causes two types of renal involvement, which are the pauci-immune type without IC deposits and the IC deposition type that involves three patterns of IC deposition in the glomeruli. The reason why IC deposits are associated with renal-limited vasculitis and not systemic vasculitis remains unclear.
BACKGROUND: Several authors have reported cases of anti-neutrophil cytoplasmic antibody (ANCA)-associated crescentic glomerulonephritis (CGN) with definite immune complex (IC) deposits, however, the clinical and pathological significance of IC deposits in patients with ANCA-associated CGN remains unclear. METHODS: Renal biopsy specimens from 28 patients with a diagnosis of CGN and positivity for anti-myeloperoxidase (MPO)-ANCA were retrospectively evaluated. Clinical data were compared between patients with IC deposits (Group A) and patients without IC deposits (Group B). RESULTS: In 12 patients (43%; Group A), IC deposits were detected in the mesangium and/or along the glomerular capillary walls, while typical pauci-immune CGN without IC deposits was found in 16 patients (57%; Group B). Compared with Group B, Group A had lower levels of MPO-ANCA (171 ± 156 vs. 352 ± 299 EU) and C-reactive protein (CRP) (0.63 ± 1.04 vs. 4.45 ± 4.00 mg/dl), as well as less pulmonary involvement (8.3% vs. 56.3%) at diagnosis. However, Group A had significantly heavier proteinuria (2.46 ± 1.67 vs. 0.76 ± 0.52 g/d). Group A was classified into three subgroups: Group A1 with mesangial IgA and C3 deposits, A2 with mesangial IgG and C3 deposits, and A3 with IgG and C3 deposits mainly in the capillary walls. CONCLUSIONS: ANCA-associated CGN causes two types of renal involvement, which are the pauci-immune type without IC deposits and the IC deposition type that involves three patterns of IC deposition in the glomeruli. The reason why IC deposits are associated with renal-limited vasculitis and not systemic vasculitis remains unclear.