A Study Using Real-world Data to Examine Outcomes in Children and Adults Who Develop a Blood Clotting Disorder Called Thrombotic Microangiopathy (TMA) After Undergoing a Hematopoietic Stem Cell Transplant (HSCT).

Inclusion Criteria: * Participant must be ≥ 28 days of age at the time of TMA diagnosis. * Body weight ≥ 5 kg at the time of TMA diagnosis. * Documented TMA on/after 01 Jan 2010 to 30 Jun 2024 with concurrent renal dysfunction with no documented alternative explanation ≤ 52 weeks from the HSCT. * Documentation of participant's vital status through 52 weeks after the date of TMA diagnosis. * Documentation of date and type of HSCT, date of TMA, absence of acute GVHD, and infection status at time of TMA diagnosis. * Documentation of at least 2 of the following: indication for most recent HSCT, serum creatinine at time of TMA diagnosis, presence of multiorgan dysfunction at time of TMA diagnosis. * Informed consent obtained if required by local regulations. Exclusion Criteria: * Medical Conditions (Ongoing at the Time of TMA Diagnosis): TTP, ST-HUS, Immune-mediated hemolysis not due to TMA, DIC, Bone marrow/graft failure of HSCT, VOD (regardless of severity), HIV infection, Sepsis that required vasopressor support. * Prior/Concomitant Therapy: Received a complement inhibitor other than eculizumab from time of suspicion of HSCT-TMA diagnosis through 52 weeks post-HSCT-TMA diagnosis.. * Other Exclusions: Participation in an investigational drug or device study for the treatment of TMA within 30 days prior to TMA diagnosis or during the 52 weeks following TMA diagnosis.