Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Phacomatosis pigmentovascularis ?
    ### Response:
    What causes phacomatosis pigmentovascularis? Phacomatosis pigmentovascularis (PPV) is thought to occur as a result of a change in the arrangement of a small piece of genetic material in a developing embryo. Because of this change some of the baby's body cells carry two copies of recessive gene mutations while the majority of his or her body cells carry only one.
    