Abstract
Eculizumab is an emerging therapy for atypical hemolytic uremic syndrome (aHUS). Early identification and treatment of recurrent aHUS after kidney transplantation requires a high clinical suspicion but results in improved graft function and patient outcome. We present a patient who developed recurrent aHUS after kidney transplantation that responded to eculizumab therapy. A kidney biopsy was performed to confirm resolution of thrombotic microangiopathy 8 weeks after eculizumab treatment initiation and revealed no features of thrombotic microangiopathy. Instead, the biopsy revealed monoclonal immunoglobulin G (IgG)4/2κ deposition in the glomerular tufts, vasculature, and atrophic tubular basement membranes. IgG4/2κ deposits are a rare pathologic finding following eculizumab therapy, and the long-term effect of these deposits on kidney function remains unknown.