Clinical Outcomes and Clinico-pathological Correlations in Lupus Nephritis with Kidney Biopsy Showing Thrombotic Microangiopathy

Objective. Renal thrombotic microangiopathy (TMA) is an uncommon pathological finding in lupus nephritis (LN), and its clinical significance remains to be defined. Methods. Twenty-four patients with lupus nephritis (LN) and renal TMA were selected from a retrospective review of 677 biopsy-proven LN patients, and compared with 48 LN controls without TMA (1:2 ratio) matched according to demographics and treatments. Results. Renal TMA was noted in 3.5% of kidney biopsies of LN. TMA was associated with a higher prevalence of anti-Ro (45.8% vs 18.8%; p = 0.016), higher Systemic Lupus Erythematosus Disease Activity Index scores (21.4 ± 8.5 vs 10.8 ± 2.3; p < 0.001), lower estimated glomerular filtration rate (eGFR; 16.8 ± 11.7 ml/min vs 77.8 ± 28.6 ml/min; p < 0.001), and a higher percentage of patients who required dialysis (37.5% vs 2.1%; p < 0.001) at the time of kidney biopsy. 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 p < 0.001; respectively]. Patients with TMA showed inferior 5-year renal survival and higher incidence of chronic kidney disease at last followup (70% and 66.6%, respectively, compared with 95% and 29.2% in controls; p = 0.023 and 0.002, respectively). The TMA group also showed lower median eGFR compared with controls [50.1 (IQR 7–132) ml/min vs 85.0 (IQR 12–147) ml/min; p = 0.003]. Five-year patient survival rate was similar between the 2 groups (87% and 98% in TMA and control group, respectively; p = 0.127). Conclusion. TMA in kidney biopsy was associated with more severe clinical and histological activity, and significantly inferior longterm renal outcome in LN.