Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Complex regional pain syndrome ?
    ### Response:
    Complex regional pain syndrome (CRPS) is a chronic pain condition that mainly affects the arms, legs, hands, and feet, but may involve the entire body. CRPS symptoms often begin after an injury. The main feature of CRPS is continuous, intense pain that is out of proportion to the severity of the injury.
    