This is a China, non-interventional, observational study and will follow the Good Phar-macoepidemiology Practices guidelines.

This study will enrol paediatric and adult patients diagnosed with aHUS who will be treated according to routine clinical practice defined by local institutional treatment guidelines/protocol. Those aHUS patients who will be treated with a supportive therapy, which does not contain eculizumab, will be monitored for up to 12 months since the ini-tial diagnosis. Patients initiated on eculizumab treatment anytime between aHUS diagno-sis until 12 months will be followed for additional 12 months, starting from the ecu initia-tion. Patient disposition, characteristics, outcomes and safety will be described for all pa-tients enrolled into this study

Inclusion Criteria:

Participants are eligible to be included in the study. Age

1. Patients of any age, who are diagnosed as aHUS by a professional physician (first epi-sode or relapse).

   Type of Patient and Disease Characteristics

2. Evidence of TMA, including thrombocytopenia, evidence of hemolysis, and kidney dys-function, based on the following laboratory findings, should be recorded within 2 weeks time frame:

   1. Platelet count < 150,000 per microliter (μL), and
   2. Mechanic hemolytic anemia evident by LDH ≥ 1.5 × upper limit of normal (ULN), and hemoglobin ≤ lower limit of normal (LLN) for age and gender and
   3. Serum creatinine level ≥ ULN in adults (≥18 years of age), or ≥ 97.5th percentile for age at screening in children (patients who require dialysis for acute kidney injury are also eligi-ble).

3. Gender: Male and/or female. Informed Consent

4. Willing and able to give written informed consent and comply with the study visit schedule as described in Section 6.2.1. For patients < 18 years of age, patient's legal guardian must be willing and able to give written informed consent and the patient must be willing to give written informed assent (if applicable as determined by the central.

Exclusion Criteria:

Participants are excluded from the study if any of the following criteria apply:

Medical Conditions

1. Patients who were diagnosed with HUS only due to Shiga toxin-producing Escherichia coli (STEC).
2. Patients who were diagnosed with TTP (ADAMTS13 activity <10%). Other Exclusions
3. Unable to give written informed consent.
4. Any medical or psychological condition that, in the opinion of the Investigator, could increase the risk to the participant by participating in the study or confound the outcome of the study.

paediatric and adult patients diagnosed with aHUS

Qualified researchers can request access to anonymized individual patient-level data from AstraZeneca group of companies sponsored clinical trials via the request portal Vivli.org. All requests will be evaluated as per the AZ disclosure commitment: https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.

"Yes", indicates that AZ are accepting requests for IPD, but this does not mean all requests will be approved.

AstraZeneca will meet or exceed data availability as per the commitments made to the EFPIA/PhRMA Data-Sharing Principles. For details of our timelines, please refer to our disclosure commitment at https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.

When a request has been approved AstraZeneca will provide access to the anonymized individual patient-level data via secure research environment Vivli.org. A Signed Data Usage Agreement (non-negotiable contract for data accessors) must be in place before accessing requested information.