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.