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
Donath landsteiner antibody is seen in? 
Select and explain. 
A. PNH, B. Waldenstrom's macroglobulinemia, C. Paroxysmal cold hemoglobinuria, D. Malaria
C: Paroxysmal cold hemoglobinuria
Answer: C: Paroxysmal cold hemoglobinuria 
Explanation: Ans. is 'c' i.e., Paroxysmal cold hemoglobinuria Paroxysmal cold hemoglobinuria (PCH) o PCH is characterized by intermittent massive intravascular hemolysis frequently with hemoglobinuria at low temprature. o The autoantibodies are of IgG class, also known as Donath-Landsteiner antibody. o These antibodies are directed against P-antigen on RBC. o Antigen antibody complex on the red blood cell activates complement. o As a result, large amount of membrane attack complex forms which destroys red cells directly --> intravascular hemolysis. o Causes are : - Syphilis, Mycoplasma, Mumps, Measles, Flu syndrome