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

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.