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': "Donath Landsteiner antibody is seen in- \nSelect and explain. \nA. PNH, B. Waldenstrom's macroglobulinemia, C. Paroxysmal cold hemoglobinuria, D. Malaria", 'role': 'user'}, {'content': 'Answer: C \nExplanation: Paroxysmal cold hemoglobinuria (PCH)\n\nPCH is characterized by intermittent massive intravascular hemolysis frequently with hemoglobinuria at low temperature.\nThe autoantibodies are of IgG class, also known as Donath-Landsteiner antibody.\nThese antibodies are directed against P-antigen on RBC.\nAntigen-antibody complex on the red blood cell activates complement.\nAs a result, a large amount of membrane attack complex forms which destroys red cells directly → intravascular hemolysis.\nCauses are: - Syphilis, Mycoplasma, Mumps, Measles, Flu syndrome', 'role': 'assistant'}]