Measurement of complement proteins may aid interpretation of pathophysiology in kidney transplant recipients with atypical hemolytic uremic syndrome.

A 53-year-old woman with kidney failure and low-titer donor-specific antibody underwent a living-unrelated donor kidney transplant. Presentation of severe thrombotic microangiopathy (TMA) resulted in early graft loss at day 8 post-transplant and initiation of hemodialysis. Thorough examination of the medical data revealed the patient to have had atypical hemolytic uremic syndrome (aHUS). Hemolytic anemia persisted for several months, even after complete embolization of the kidney graft. The patient subsequently received prophylactic eculizumab treatment and underwent a successful second transplant from a familial donor. Withdrawal of eculizumab resulted in development of TMA in the second graft, while reintroduction of eculizumab reversed the TMA. We examined complement-related profiles over time, and serial measurement of factors such as factor Ba, soluble C5b-9, and C3, and of total complement activity (CH50), clearly reflected the underlying pathophysiological condition and treatment status of the patient before, during, and after transplant. Longitudinal observation of complement protein levels may therefore aid in identifying candidates for kidney transplant who are at risk of aHUS, and monitoring patient status during transplant and follow-up.