ANCA-associated nephritis without crescent formation has atypical clinicopathological features: a multicenter retrospective study

Background Although crescentic glomerulonephritis is a hallmark of ANCA-associated nephritis, the clinicopathological features of ANCA-associated nephritis without crescent formation remain to be elucidated. Methods We enrolled 146 Japanese ANCA-associated vasculitis (AAV) patients subjected to renal biopsy in 16 hospitals from 2001 to 2018, and compared those with and without crescent formation (C + and C- groups). The primary endpoint was end-stage renal disease (ESRD) and/or death. Results C- group comprised 25 (17.1%) subjects. They had better renal function at the time of renal biopsy [estimated glomerular filtration rate (eGFR); median 41.7 vs 27.5 ml/min/1.73 m(2),p < 0.01] with minor urinary abnormalities but had a higher serum C-reactive protein level (8.8 vs 5.4 mg/dl,p = 0.01) and frequency of extra-renal lesions of AAV (76.0% vs 48.8%,p = 0.02) than C + group. Pathologically, C- group had a higher frequency of arteritis (40.0% vs 16.5%,p < 0.01). Kaplan-Meier method with log-rank tests showed no significant difference in renal and life prognosis combined, regardless of crescent formation. Multivariate Cox regression analysis revealed baseline eGFR, sclerotic class, and extra-renal lesions to be risk factors of ESRD and death combined. Competing risk analysis showed baseline eGFR and sclerotic class to be associated with ESRD, whereas baseline eGFR and extra-renal lesions were associated with death. Conclusion ANCA-associated nephritis without crescent formation had different clinicopathological features from those with crescent formation, suggesting an atypical subtype of ANCA-associated nephritis. Despite the better renal function at the time of renal biopsy, these results suggest that this subtype requires especially careful attention, especially in the presence of extra-renal involvement.