Open Label Controlled Trial of Eculizumab in Adult Patients With Plasma Therapy-Resistant aHUS

Exclusion Criteria: 1. TTP, (defined as ADAMTS-13 activity \<5%) from an historical observation (prior to initiation of plasma therapy) or as tested at the screening visit by the central laboratory 2. Malignancy within 5 years of screening 3. Typical HUS (Shiga toxin +) 4. Known HIV infection 5. Identified drug exposure-related HUS. 6. Infection-related HUS 7. HUS related to bone marrow transplant 8. HUS related to vitamin B12 deficiency 9. Renal function status requiring chronic dialysis 10. Patients with a confirmed diagnosis of sepsis 11. Presence or suspicion of active and untreated systemic bacterial infection that, in the opinion of the Investigator confounds an accurate diagnosis of aHUS or impedes the ability to manage the aHUS disease 12. Pregnancy or lactation 13. Unresolved meningococcal disease 14. Known Systemic Lupus Erythematosus (SLE) or antiphospholipid antibody positivity or syndrome 15. Any medical or psychological condition that, in the opinion of the investigator, could increase the patient's risk by participating in the study or confound the outcome of the study 16. Patients who have received previous treatment with eculizumab 17. Patients receiving IVIG within 8 weeks or Rituximab therapy within 12 weeks of screening. 18. Patients receiving other immunosuppressive therapies such as steroids, mTOR inhibitors or tacrolimus are excluded unless: \[1\] part of an established post-transplant anti-rejection regime, \[2\] patient has confirmed anti-CFH antibody requiring immunosuppressive therapy, and \[3\] dose of such medications have been unchanged for at least 4 weeks prior to the screening period or \[4\] patient is experiencing an acute aHUS relapse immediately after transplant 19. Patients receiving Erythrocyte Stimulating Agents (ESAs) unless already on a stable dose for at least 4 weeks prior to the screening period, or a washout period of at least 2 weeks from the last dose of ESA therapy. 20. Participation in any other investigational drug trial or exposure to other investigational agent, device, or procedures beginning 4 weeks prior to screening and throughout the entire trial. 21. Hypersensitivity to eculizumab, to murine proteins or to one of the excipients