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): 20.0-999.0,  Aplastic Anemia Diagnosis of Aplastic Anemia (AA) confirmed by peripheral blood and bone-marrow examinations, etc Refractory to at least one course of immunosuppressive therapy including horse or rabbit anti-human thymocyte immunoglobulin (ATG); or ineligible for ATG treatment and refractory to cyclosporin (CyA) Thrombocytopenia defined as a platelet count of ≤ 30 × 10^9/L Preserving main organ function as a result of screening as follows Total bilirubin: < 1.5 times the upper limit of the laboratory normal range Alanine aminotransferase: < 3.0 times the upper limit of the laboratory normal range Aspartate aminotransferase: < 3.0 times the upper limit of the laboratory normal range Creatinine value: ≤ 2.0 mg/dL An Eastern Cooperative Oncology Group performance status score of 0 to 2 at screening ≥ 20 years of age at the time of obtaining informed consent  Concurrent active infection not adequately responding to appropriate therapy Bone marrow reticulin grade of ≥ 2 based on the grading scale for reticulin indicated in Bone Marrow Pathology (2nd edition) Proportion of blasts in bone marrow > 2% Previous or concurrent active malignancies, other than localized tumors diagnosed more than one year previously and treated surgically with curative intent (basal cell carcinoma; or surgically resected in situ carcinoma of the cervix with an apparent success of ≥ 12 months prior to enrollment; as well as other cancers which have not been treated and remained disease-free for at least 5 years before enrollment are eligible) Clinically significant cardiac disease (class III or IV of the New York Heart Association classification; unstable angina pectoris; myocardial infarction within 6 months before enrollment; cardiac disease accompanied by angioplasty or stenting within 6 months before enrollment; or clinically significant cardiac arrhythmias) or uncontrollable hypertension Arterial or venous thrombosis within one year before enrollment Positive for anti-human immunodeficiency virus antibodies, hepatitis B surface antigen, or hepatitis C virus-RNA at screening Thrombocytopenia due to any other cause (e.g., myelodysplastic syndrome, idiopathic thrombocytopenic purpura, or liver cirrhosis) Patients with acute myeloblastic leukemia or chronic myelomonocytic leukemia Concurrent occurrence of hemolytic predominant paroxysmal nocturnal hemoglobinuria (Hemolytic predominant is defined as lactate dehydrogenase > 1.5 times the upper limit of the laboratory normal range)