Snapshot A 25-year-old pregnant woman presents with fatigue and abdominal pain in the emergency room. She reports feeling unwell for the past few days. Every morning, she notices that her urine is tea-colored, which slowly resolves throughout the day. She has a low-grade fever. On physical exam, her skin is jaundiced, her liver edge is palpable, and she has abdominal tenderness to palpation. Her physicians are suspicious of Budd-Chiari syndrome. Introduction Clonal stem cell defect from mutation in hematopoietic stem cell Pathogenesis mutation in PIGA gene defect in glycosylphosphatidylinositol (GPI) anchors CD55 (decay-accelerating factor) and CD59 on RBC membrane these protect RBC from complement DAF inhibits C3 convertase complement-mediated destruction of RBCs ultimately, terminal membrane attack complex formation "PNH Thrombosis" Pancytopenia with Nocturnal build up of dark urine Coombs negative Hemolytic anemia (complement-mediated) venous Thrombosis Acute hemolysis often triggered by stress, infection, surgery, and other inflammatory states May cause aplastic anemia myelodysplasia acute leukemia Presentation Symptoms/physical exam episodic dark urine with first urine of the day caused by hemoglobin hemolytic anemia: pallor, fatigue, tachycardia, jaundice, and gross hematuria thrombocytopenia: mucosal bleeding, petechiae,and ecchymoses leukemia: infections thrombosis renal impairment Evaluation Flow cytometry – most accurate test CD55/59-negative RBCs Labs anemia thrombocytopenia leukopenia Differential Diagnosis Aplastic anemia Myelodysplasia Treatment Eculizumab inactivates C5 in complement pathway decreases red cell destruction complement inhibitor must vaccinate all against Neisseria due to increased risk Allogeneic bone marrow transplant Supportive therapy folic acid transfusions as needed Prognosis, Prevention, and Complications Prognosis improved with use of eculizumab Complications renal insufficiency thromboembolism 5% develop myelodysplasia 2.5% develop acute leukemias