Below is an instruction from Human. Write a response.
    ### Instruction:
    How to diagnose Pseudoxanthoma elasticum ?
    ### Response:
    What testing is available to identify unaffected carriers of pseudoxanthoma elasticum? When considering carrier testing for unaffected relatives of individuals with pseudoxanthoma elasticum (PXE), it is most useful to begin by testing an affected family member for mutations in the ABCC6 gene.
    