Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) horizontal gaze palsy with progressive scoliosis ?
    ### Response:
    Horizontal gaze palsy with progressive scoliosis (HGPPS) is a disorder that affects vision and also causes an abnormal curvature of the spine (scoliosis). People with this condition are unable to move their eyes side-to-side (horizontally). As a result, affected individuals must turn their head instead of moving their eyes to track moving objects.
    