Autoimmune Hemolytic Anemia Complicated by Portal Vein Thrombosis in a Pediatric Liver Transplant Recipient: A Case Report.

Post-transplant autoimmune hemolytic anemia (AIHA) occurs in approximately 1% to 3% of pediatric liver transplant recipients. Its co-occurrence with portal vein thrombosis (PVT) is exceedingly rare and potentially life-threatening. We report a 10-month-old female who underwent living-donor liver transplantation for biliary atresia and presented with AIHA 5 months later. Laboratory evaluation revealed severe hemolytic anemia (hemoglobin 7.5 g/dL), markedly elevated lactate dehydrogenase (1751 IU/L), hyperbilirubinemia (total bilirubin 4.92 mg/dL), thrombocytopenia (75 × 103/μL), prolonged PT/INR, critically reduced Protein S activity (48.1%), and elevated D-dimer (3.78 mg/L; 7.6 × upper normal). A strongly positive Direct Antiglobulin Test confirmed AIHA. Abdominal computed tomography demonstrated hepatomegaly with portal vein thrombosis, confirmed by color-flow Doppler ultrasonography with turbulent, reduced flow. Tacrolimus dose was reduced and simultaneous high-dose methylprednisolone (4 mg/kg/d intravenously), rituximab, and therapeutic heparin were initiated. Complete portal vein recanalization was confirmed by Doppler on Day 5, with full immunologic remission (Direct Antiglobulin Test-negative) thereafter. This case demonstrates that post-transplant AIHA can precipitate PVT through a hemolysis-driven hypercoagulable cascade involving Protein S consumption, thrombocytopenia, and pro-coagulant erythrocyte microparticle release. Systematic coagulation profiling and Doppler ultrasonography at AIHA onset are mandatory in pediatric liver transplant recipients to prevent potentially fatal vascular complications.