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.