This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': 'Intravascular hemolysis occurs in: \nSelect and explain. \nA. Hereditary spherocytosis, B. Autoimmune haemolytic anemia, C. Paroxysmal nocturnal hemoglobinuria, D. Thalassemia', 'role': 'user'}, {'content': 'Answer: C \nExplanation: PNH is a disease that results from acquired\xa0mutations in the phosphatidylinositol glycan complementation group A gene (PIGA), an enzyme that is essential for the synthesis of certain cell surface proteins.\nRed cells, platelets, and granulocytes deficient in these GPI-linked factors are abnormally susceptible to lysis by complement. In red cells, this manifests as intravascular hemolysis, caused by the C5b-C9 membrane attack complex.\n\n\xa0\n\nThe triad of hemolysis, pancytopenia and thrombosis is unique to PNH.\nThrombosis is the leading cause of disease-related death in PNH.\nPNH is best made with flow cytometry in which there is presence of bimodal distribution of the red cells.', 'role': 'assistant'}]