Objectives: To retrospectively investigate the clinical and histological features and outcomes of ANCA-associated glomerulonephritis (AAGN) with different ANCA serotypes.
Method: A total of 467 AAGN patients were divided into MPO-AAGN (MPO) and PR3-AAGN (PR3) groups according to ANCA serotype. Clinical and histological features and renal outcomes were compared.
Results: In this study, 429 (91.9%) patients tested positive for MPO-ANCA, and 38 (8.1%) for PR3-ANCA. The median age at diagnosis (P = 0.017) and proportion of females (P = 0.003) were higher in the MPO group. Joint (P < 0.001), ENT (P = 0.000), skin (P = 0.007), and eye (P = 0.014) involvements were more common in the PR3 group. Compared with that in the PR3-group, a higher proportion of patients in the MPO group had microscopic polyangiitis (P = 0.000), and a lower proportion of exhibited granulomatosis with polyangiitis (P = 0.000). Patients in the MPO group also exhibited lower BVAS scores (P = 0.003) and higher serum albumin levels (P = 0.009). Histologically, a lower proportion of MPO patients had crescentic glomerulonephritis (P = 0.028) and acute tubule-interstitial lesion scores (P = 0.007), but a higher proportion of these patients exhibited mixed class glomerulonephritis (P = 0.032) than in the PR3 group. The relapse rate was lower (P = 0.020), and the 5-year relapse-free survival rate (P = 0.003) was higher in the MPO group than in the PR3 group. However, the 5-year renal survival rates (P = 0.106) were not significantly different.
Conclusions: MPO-ANCA was predominant in Chinese patients with ANCA-associated vasculitis and renal disease. The epidemiological characteristics, extra-renal involvement, and histopathological classes and outcomes were different between MPO-positive and PR3-positive patients, implying that they might be two different disease entities.
Keywords: Antineutrophil cytoplasmic antibody; Glomerulonephritis; Myeloperoxidase; Proteinase 3.