Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes 15q11.2 microdeletion ?
    ### Response:
    What causes a 15q11.2 microdeletion? A 15q11.2 microdeletion may occur randomly for the first time in an affected person (a de novo mutation), or it may be inherited from a parent with the microdeletion. A blood test to look at the parents' chromosomes is needed to find out how the microdeletion occurred.
    