Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Rh deficiency syndrome ?
    ### Response:
    The Rh deficiency syndrome, also known as Rh-null syndrome, is a blood disorder where people have red blood cells (RBCs) lacking all Rh antigens. The Rh antigens maintain the integrity of the RBC membrane and therefore, RBCs which lack Rh antigens have an abnormal shape.
    