Patient description: The patient is a 23-year-old man who came to the hospital with high blood pressure (175/95 mmHg) and signs of septicemia. He developed respiratory failure requiring mechanical ventilation and renal failure requiring hemodialysis. His blood smear showed microangiopathic hemolytic anemia and thrombocytopenia. His blood tests revealed elevated lactate dehydrogenase and reduced human complement C3 levels with a normal coagulation profile. He was diagnosed with atypical hemolytic uremic syndrome. He was treated with plasma exchange and corticosteroids. He has been previously vaccinated with meningococcal group ACWY conjugate vaccine and meningococcal group B vaccine. The genetic survey revealed ADAMTS13 >10%.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Atypical Hemolytic-Uremic Syndrome Patient must be willing and able to give written informed consent. 2. Patient's age > 18 years. 3. Patients exhibit thrombocytopenia, hemolysis and elevated Serum Creatinine. 4. Patients with diagnosis of aHUS with or without an identified complement regulatory protein genetic abnormality or anti-complement factor antibody and for whom etiologies of hemolytic uremic syndrome have been ruled out as confirmed in the 5. Female patients of childbearing potential must be practicing an effective, reliable and medically approved contraceptive regimen during the entire duration of the study, including the follow-up period. At the time of the last follow-up visit, patients must agree to continue to use adequate contraception methods for up to 5 months following discontinuation of eculizumab treatment. 6. Able and willing to comply with study procedures 1. Chronic dialysis. 2. Prior eculizumab use or hypersensitivity to eculizumab, to murine proteins or to one of the excipients. 3. Known familial a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS-13) deficiency (ADAMTS-13 <5%). 4. Typical Hemolytic-Uremic Syndrome (HUS) (known Shiga toxin +). 5. History of malignancy within 5 years of screening. 6. Known human immunodeficiency virus (HIV) infection. 7. Identified drug exposure-related hemolytic-uremic syndrome (HUS). 8. Infection-related HUS. 9. HUS related to bone marrow transplant (BMT). 10. HUS related to vitamin B12 deficiency. 11. Known Systemic Lupus Erythematosus (SLE) or antiphospholipid antibody positivity or syndrome. 12. Patients with a confirmed diagnosis of sepsis defined as positive blood cultures within 7 days of the screening visit and not treated with antibiotics to which the organism is sensitive. 13. 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. 14. Pregnancy or lactation. 15. Unresolved systemic meningococcal disease. 16. 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. 17. Patients receiving chronic intravenous immunoglobulin (IVIg) within 8 weeks or chronic Rituximab therapy within 12 weeks of screening visit. 18. Patients receiving other immunosuppressive therapies such as steroids, mechanist target of rapamycin (mTOR) inhibitors, calcineurin inhibitors (e.g., cyclosporine or tacrolimus) are excluded unless: [1] part of an established post-transplant anti-rejection regime, or [2] patient has confirmed anti-Complement Factor Antibodies requiring immunosuppressive therapy, or [3] steroids are being used for a condition other than aHUS (example asthma). 19. Participation in any other investigational drug trial or device trial, or procedures beginning 4 weeks prior to screening and throughout the entire trial