Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Cold agglutinin disease ?
    ### Response:
    Cold agglutinin disease is a rare type of autoimmune hemolytic anemia in which the body's immune system mistakenly attacks and destroys its own red blood cells. When affected people's blood is exposed to cold temperatures (32 to 50 F), certain proteins that normally attack bacteria (IgM antibodies) attach themselves to red blood cells and bind them together into clumps (agglutination).
    