Below is an instruction from Human. Write a response.
    ### Instruction:
    How to diagnose Fatal familial insomnia ?
    ### Response:
    Is genetic testing available for fatal familial insomnia? Yes, genetic testing is available for PRNP, the gene known to cause fatal familial insomnia (FFI). Carrier testing for at-risk relatives and prenatal testing are possible if the disease-causing mutation in the family is known.
    