Complement Prospective Evaluation of Thrombotic Microangiopathy on Endothelium

Inclusion Criteria: * Males or females at least 18 years of age; * Have acute kidney injury, defined as estimated GFR \<45 mL/min/1.73m2; * Have documented TMA either on peripheral blood, defined as Coombs negative microangiopathic hemolytic anemia (hematocrit \<30%, hemoglobin \<6.5 mmol/L \[\<10 g/dL\], lactate dehydrogenase \>500 U/L, and either schistocytes on peripheral blood smear or undetectable haptoglobin), and platelets \<150,000 per µL, or kidney biopsy; * Have primary atypical HUS or a coexisting condition linked to complement dysregulation: * Hypertensive emergency, defined as SBP/DBP of \>180/120 mmHg and impending organ damage secondary to hypertension (at least one of the following: neurologic disease, hypertensive retinopathy grade III and/or IV, left ventricular hypertrophy); OR * Pregnancy, including 12 weeks postpartum; OR * Kidney donor recipient; OR * Systemic auto-immune disease associated with TMA, including systemic sclerosis, systemic lupus erythematosus, anti-phospholipid syndrome; * Have the ability to understand the requirements of the study, provide written informed consent, and comply with the study protocol procedures. Exclusion Criteria: * Have secondary causes of hypertensive emergency, including renovascular hypertension, Cushing syndrome, aldosteronism, pheochromocytoma, thyroid disease; * Have a nephropathy not related to thrombosis on kidney biopsy; * Have ADAMTS13 deficiency, defined as ADAMTS13 activity \<10%; * Have a positive stool culture for Shiga toxin producing bacteria; * Have positive serologic test for viral infections, including HIV and CMV; * Have a history of malignant disease, excluding non-melanoma skin cancer; * Have a history of bone marrow or solid organ transplantation, excluding kidney transplantation; * Received at least one of the following agents: chemotherapeutics, sirolimus, anti-VEGF agents; * Have a history of recent past exposure to illicit drug(s).