Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Lichen planus pigmentosus ?
    ### Response:
    Lichen planus pigmentosus (LPP) is a rare form of lichen planus. It is characterized by oval or irregularly shaped brown to gray-brown macules and patches on the skin. Areas that are exposed to sun such as the forehead, temples and neck are most commonly affected.
    