Postpartum Atypical Hemolytic Uremic Syndrome Complicating β-Thalassemia Intermedia: A Case Report and Literature Review

Background: Atypical hemolytic uremic syndrome (aHUS) is a life-threatening thrombotic microangiopathy driven by uncontrolled activation of the complement alternative pathway, with pregnancy triggering 10–20% of cases (pregnancy-associated aHUS, p-aHUS). Thalassemia, a chronic hemolytic anemia, creates a state of subclinical complement dysregulation; however, its clinical association with p-aHUS has rarely been reported. Methods: This study presents a 27-year-old primigravida with β-thalassemia intermedia requiring transfusions during pregnancy (CD17 heterozygote) who developed severe postpartum hemorrhage (1760 mL) after vaginal delivery. Over postpartum days 0–4, the patient was monitored for hematological and renal parameters. Laboratory investigations included peripheral smear, ADAMTS13 activity assay, direct Coombs test, and sC5b-9 complement level measurement. Results: Over postpartum days 0–4, the patient developed microangiopathic hemolytic anemia (hemoglobin nadir 46 g/L, lactate dehydrogenase peak 3436 U/L), thrombocytopenia (platelet nadir 31 × 109/L), and acute kidney injury (creatinine peak 663 μmol/L). Peripheral smear showed 4% schistocytes. Subsequent detection revealed normal ADAMTS13 activity (90%), negative direct Coombs test, and elevated sC5b-9 (384.95 ng/mL; normal < 340). The diagnosis of p-aHUS was confirmed, and the patient received hemodialysis and recovered within three months. Conclusions: These findings suggest that chronic complement dysregulation secondary to thalassemia, combined with pregnancy-related complement stress and postpartum hemorrhage, may contribute to the development of p-aHUS. Therefore, thalassemia should be considered a potential sensitizing condition for p-aHUS, warranting close monitoring and complement evaluation in such patients.