Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) progressive pseudorheumatoid dysplasia ?
    ### Response:
    Progressive pseudorheumatoid dysplasia (PPRD) is a joint disease that worsens over time. This condition is characterized by breakdown (degeneration) of the cartilage between bones (articular cartilage). This cartilage covers and protects the ends of bones, and its degeneration leads to pain and stiffness in the joints and other features of PPRD.
    