Pregnancy-Associated Atypical Hemolytic Uremic Syndrome With Kidney Recovery Despite Delayed Initiation of Complement Blockade.

Atypical hemolytic uremic syndrome (aHUS) is a complement-mediated thrombotic microangiopathy (TMA) characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury, and pregnancy is a recognized trigger, particularly in the third trimester and postpartum period. We report a 29-year-old primigravida at 33 weeks' gestation who presented with severe acute kidney injury (AKI), thrombocytopenia, anemia, elevated lactate dehydrogenase, and hyperbilirubinemia with otherwise normal liver enzymes. The ADAMTS13 activity was normal, and autoimmune serologies were negative. She required urgent hemodialysis and underwent emergency cesarean section for maternal indications; however, renal failure persisted postpartum with dialysis dependence. Kidney biopsy demonstrated thrombotic microangiopathy with arteriolar fibrin thrombi. Genetic testing identified a heterozygous pathogenic splice-site variant in complement factor H, supporting the diagnosis of complement-mediated aHUS. Complement inhibition with eculizumab was initiated approximately five weeks after presentation and later transitioned to ravulizumab. Despite delayed therapy and initial dialysis dependence, she achieved dialysis independence five weeks after initiation of complement blockade, with partial renal recovery and normalization of platelet count. This case emphasizes the need to consider complement-mediated TMA in pregnant patients with severe renal dysfunction disproportionate to liver enzyme abnormalities and demonstrates that meaningful renal recovery remains possible even when dialysis is required, and complement inhibition is not initiated immediately.