Differential Diagnosis of Thrombotic Microangiopathy in a Patient with Systemic Lupus Erythematosus: A Case Report

Introduction: Systemic lupus erythematosus (SLE) is a chronic autoimmune disease of unknown cause. Kidney involvement is common usually due to immune complex-mediated glomerular disease; however, vascular disease can also occur and generally adversely affect the prognosis and increase mortality. Thrombotic microangiopathy (TMA) is a severe renal vascular injury presenting with progressive life-threating thrombocytopenia, microangiopathic hemolytic anemia, and renal failure. The differential diagnosis of TMA in a patient with SLE includes antiphospholipid antibody syndrome (APS), thrombotic thrombocytopenic purpura (TTP), complement-mediated atypical hemolytic uremic syndrome (aHUS), drug-mediated TMA (particularly due to calcineurin inhibitor toxicity) and malignant hypertension. Case Description: We present the clinical case of a 38-year-old woman with SLE diagnosed eight years ago; she was on treatment with hydroxychloroquine 200 mg/day and prednisone 5 mg/day. She was admitted because of abdominal pain, nausea, headache, blurred vision and severe hypertension. Serum creatinine was 3,35 mg/dl (previously normal), hemoglobin 9.2 g/dL, platelets 75.000, lactate dehydrogenase 558 U/L, with no schistocytes in blood smear. Lupus Nephritis was suspected at admission due to her backgrounds, however, complement values were normal: C3 107 mg/dL, C4 22 mg/dl and anti DNA antibodies was negative, urine analysis showed 6 erythrocytes per high power field, proteinuria +, no crystals, no casts and urine protein resulted in 2.6 g/day. Kidney biopsy showed in optic microscopy severe thickening of arterioles with some lumens completely obliterated. Immunofluorescence stain was completely negative. Final pathologic diagnosis was thrombotic microangiopathy with glomerular and arterials vessels involvement. Discussion: This patient had a (+) lupus anticoagulant. The most probably cause of TMA was (APS) nephropathy, anticoagulation and rituximab were started.Myointimal proliferation (hematoxylin and eosin)