Lupus nephritis combined with renal injury due to thrombotic thrombocytopaenic purpura-haemolytic uraemic syndrome

Abstract

Background. Thrombotic thrombocytopaenic purpura–haemolytic uraemic syndrome (TTP–HUS) in SLE was reported mainly in isolated case reports. The aim of this study is to investigate the clinical and pathological features, outcome and possible pathogenesis of TTP–HUS in patients with lupus nephritis. Methods. Clinical and renal histopathological data of patients with lupus nephritis were reviewed for clinical and pathological evidence of both TTP–HUS and renal thrombotic microangiopathy (TMA). Serum ADAMTS-13 activity and ADAMTS-13 autoantibodies were further studied. Results. Seven patients with evidence of both TTP–HUS and renal TMA were identified in 353 patients with lupus nephritis. In comparison with 55 patients with lupus nephritis without TTP–HUS, those with TTP–HUS had a higher prevalence of acute renal failure and worse renal outcome. The serum ADAMTS-13 activity was significantly lower in patients with both lupus nephritis and TTP–HUS than in patients with lupus nephritis only and in normal control (40% versus 69%, P = 0.012; 40% versus 81%, P < 0.001, respectively). The prevalence of ADAMTS-13 autoantibodies was significantly higher in patients with both lupus nephritis and TTP–HUS than in patients with lupus nephritis only and in normal control (6/7, 86% versus 10/55, 18%, P < 0.001; 6/7, 86% versus 0, P < 0.001, respectively). After clinical remission, the serum ADAMTS-13 activity of the seven patients with TTP–HUS increased significantly (40% versus 63%, P < 0.001) and five out of the six patients with positive ADAMTS-13 autoantibodies turned negative. Conclusions. ADAMTS-13 autoantibodies might play an important role in the pathogenesis of TTP–HUS associated with lupus nephritis. The long-term outcome seems to be worse in patients with both TTP–HUS and lupus nephritis than in patients with lupus nephritis alone.