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. The key symptom of CRPS is continuous, intense pain out of proportion to the severity of the injury, which gets worse rather than better over time. CRPS most often affects one of the arms, legs, hands, or feet.
    