What is paroxysmal cold hemoglobinuria?

• Donath-Landsteiner hemolytic anemia • Autoantibody (IgG) binds to the red blood cell (RBC) P antigen in the cold and fixes complement. • Upon warming, the antibody dissociates and complement lyses the RBCs, leading to intravascular hemolysis. • Induced by acute infections (often viral), chronic syphilis, or states of immune dysregulation