Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Polycythemia Vera ?
    ### Response:
    Polycythemia vera (POL-e-si-THEE-me-ah VAY-rah or VE-rah), or PV, is a rare blood disease in which your body makes too many red blood cells.
                
The extra red blood cells make your blood thicker than normal. As a result, blood clots can form more easily.
    