Although atypical HUS (aHUS) represents the first cause of recurrent posttransplant TMA, etiologies of de novo posttransplant TMA commonly include immunosuppressive medications (i.e., CNI and mTOR inhibitors), antibody-mediated rejection, viral infections, and malignant hypertension.2 The gene discussed is MTOR; the disease is atypical hemolytic-uremic syndrome.