Atypical hemolytic uremic syndrome (aHUS) is a rare, progressive, and life-threatening disease that occurs at any age, with incidence rate of 0.75 to 2.0 cases per million population per year. aHUS is a thrombotic microangiopathy (TMA) commonly caused by dysregulation of the complement system, affecting several organs, especially the kidneys. aHUS can be familial or sporadic, and approximately 50% to 60% of patients have specific identifiable genetic complement mutations and antibodies.

Although aHUS is a rare disease, it has a significant impact on the quality of life because of its poor prognosis: a 25% global mortality rate; more than 50% of untreated patients advance to endstage renal disease (ESRD); and more than 75% of adults with renal failure require prompt dialysis. The risk of relapse is also high in many patients, either in the native or transplanted kidneys, so long-term management and close monitoring are essential.

Advancements in aHUS therapies, especially the availability of anti-complement therapy, have enhanced the natural course of aHUS through hematologic remission induction, kidney function stabilization or improvement, and graft failure prevention. Since complement inhibitors are still unavailable in Egypt, it is important to understand the aHUS manifestations of pediatrics and adults in Egyptian hospitals, aiming for early diagnosis and proper management.

In this study, we primarily aim to describe the aHUS burden on the patients by gathering their demographic and clinical characteristics, documented disease course, and long-term complications. Our secondary objectives include an estimate of the prevalence of patients diagnosed with aHUS out of all patients with TMA and gathering information about the clinical outcomes of available therapies in real-world settings, as there is no data from the country on aHUS management.

Inclusion Criteria:

• Male or female patients aged one month or older who have been diagnosed with TMA between 01-Jan-2010 and 31-Dec-2023.

Exclusion Criteria:

• None. All records of patients with TMA will be screened for aHUS diagnosis.

Patients diagnosed with TMA between 01-Jan-2010 and 31-Dec-2023 regardless of administered treatment. Medical records of all patients fulfilling the eligibility criteria will be collected.

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.

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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 rerefer to our disclosure commitment at https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.

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