Based on the detection of severe ADAMTS13 deficiency, 35 patients (81%) were diagnosed with acquired TTP, whereas the remaining 8 patients were ultimately diagnosed with complement-mediated HUS (n = 3), TMA secondary to cancer (n = 3) or TMA of unknown etiology (n = 2). The gene discussed is ADAMTS13; the disease is thrombotic thrombocytopenic purpura.