Clinicopathologic characteristics and outcomes of renal thrombotic microangiopathy in anti-neutrophil cytoplasmic autoantibody-associated glomerulonephritis

Abstract

Background and objectives Thromboticmicroangiopathy (TMA) in ANCA-associated vasculitis (AAV) has been mainly reported in isolated case reports. The aim of this study was to analyze clinical and pathologic characteristics and prognosis of patients with renal TMA in ANCA-associated GN in a large cohort of Chinese patients. Design, setting, participants, & measurements Clinical and renal histopathologic data of 220 patients with biopsy-proven ANCA-associated GNfrom 1996 to 2013 were retrospectively analyzed. Patientswere followed up for a median period of 32 (interquartile range [IQR], 12–65) months, and outcomes of patients were analyzed. ResultsAmong the 220 patientswithANCA-associatedGN, 30were identified having concomitant renalTMA by pathologic evaluation. Compared with the non-TMA group, patients with renal TMA presented with more severe renal injury, as evidenced clinically by a higher level of serum creatinine at diagnosis (5.0 [IQR, 3.5–9.0] versus 3.2 [IQR, 1.7–6.8] mg/dl; P=0.02) and pathologically by a higher percentage of cellular crescents (15.0% [IQR, 6.9%–34.9%] versus 6.9% [IQR, 0%–21.1%]; P=0.04) and more severe interstitial infiltration (2 [IQR, 2–2] versus 2 [IQR, 1–2]; P=0.03) in renal biopsies. Furthermore, multivariate analysis showed that renal TMAwas independently associated with mortality of patientswith AAV after adjusting for age, sex, initial serum creatinine, tubular atrophy, and interstitial fibrosis (hazard ratio, 1.92; 95% confidence interval, 1.08 to 3.41; P=0.03) or for age, sex, the histopathologic classification scheme proposed by Berden et al. (J AmSoc Nephrol 21: 1628–1636, 2010), tubular atrophy, and interstitial fibrosis (hazard ratio, 1.95; 95% confidence interval, 1.07 to 3.55; P=0.03). Conclusions Renal TMA in ANCA-associated GN is not rare and presents with more severe renal injury. Renal TMA is independently associated with all-cause mortality in patients with AAV.