Clinical Characteristics and outcomes of lupus nephritis patients with kidney biopsy showing thrombotic microangiopathy

Abstract

INTRODUCTION AND AIMS: Renal thrombotic microangiopathy (TMA) is an uncommon pathological finding in lupus nephritis (LN), and its clinical significance remains to be established. METHODS: We retrospectively reviewed 677 patients with kidney biopsy showing lupus nephritis (LN), followed at Queen Mary Hospital, Hong Kong or Peking Union Medical College Hospital, China. Patients with renal TMA and those without renal TMA (Controls, matched according to demographics and treatment, in 1:2 ratio) were compared focusing on clinical features and outcome. RESULTS: Twenty-four patients (3.5%) with renal TMA and 48 Controls were included, with follow-up of 48.6±31.5 and 49.2±23.8 months respectively from the time of kidney biopsy. TMA patients showed a higher rate of anti-Ro seropositivity (45.8% vs. 18.8%, p=0.016), higher SLEDAI scores (21.4±8.5 vs. 10.8±2.0, p<0.001), worse eGFR (16.8±11.7 ml/min vs. 77.8±28.6 ml/min, p<0.001), and a higher proportion requiring dialysis (37.5% vs. 2.1%, p<0.001) at presentation. Activity and chronicity indices [median (range)] were higher in the TMA group - 11 (2-19) and 3(1-8) respectively, compared with 7 (0-15) and 1 (0-3) in Controls, p=0.004 and <0.001. TMA group showed inferior renal survival, higher incidence of chronic kidney disease, and lower median eGFR at last follow-up (5-year renal survival 70%, 66.6% CKD at last follow-up, median eGFR 50.1 ml/min with IQR 7-132 ml/min) compared with Controls (95%, 29.2%, and 85.0 ml/min with IQR 12-147 ml/min; p=0.023, 0.002 and 0.003 respectively). There was no difference in patient survival between the two groups (p=0.127). CONCLUSIONS: Renal biopsy showing TMA was associated with more severe renal impairment at presentation and worse long-term renal outcome in LN.