Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the genetic changes related to psoriatic arthritis ?
    ### Response:
    The specific cause of psoriatic arthritis is unknown. Its signs and symptoms result from excessive inflammation in and around the joints. Inflammation occurs when the immune system sends signaling molecules and white blood cells to a site of injury or disease to fight microbial invaders and facilitate tissue repair.
    