Thrombotic microangiopathy (TMA), a rare but serious complication of systemic lupus erythematosus (SLE), is associated with poor outcomes to conventional immunosuppressive therapy. Recently, eculizumab, a humanised monoclonal antibody that blocks the complement factor 5, has been known to effectively treat atypical haemolytic uremic syndrome (aHUS). Here, we report a case of aHUS co-existing with lupus nephritis that was successfully treated with eculizumab.

A 13-year-old girl presented with a 3-day history of edema and reduced urine output and was admitted with anuria on the day of hospitalization. Initial laboratory tests have shown thrombocytopaenia, microangiopathic haemolytic anaemia, and acute kidney injury. Immunologic tests were consistent with SLE. Renal biopsy indicated lupus nephritis class IV-G(A/C) combined with thrombotic microangiopathy (TMA), and no gene mutations were detected in the genetic analysis. Initial treatment involved hemodialysis and high-dose methylprednisolone sodium succinate pulse therapy, which led to improvements in renal function and thrombocytopenia. However, renal function did not show further improvement after the second pulse of methylprednisolone sodium succinate and cyclophosphamide. Laboratory tests revealed elevated C5b-9 levels, ADAMTS13 activity was normal and ADAMTS13 inhibitory antibodies was negative. treated with two of doess eculizumab., combined with cyclophosphamide at a dose of 10 mg/m² once every two weeks.

During the second round of cyclophosphamide pulse therapy, the patient’s renal function and creatinine clearance were normal, urine color was yellow, and hemoglobin, complement, erythrocyte sedimentation rate, and C-reactive protein returned to normal. After eight rounds of cyclophosphamide pulse therapy, oral prednisone was gradually tapered from 50 mg once daily to 10 mg once daily, and urine protein quantification gradually decreased from 2.24 g to 0.24 g per 24 hours. While on oral amlodipine, blood pressure was maintained at around 110/70 mmHg.

Clinical suspicion of aHUS in patients with lupus nephritis is important for early diagnosis and prompt management. Timely administration of eculizumab should be considered as a treatment option for aHUS in lupus nephritis patients to yield optimal therapeutic outcomes.