Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) X-linked creatine deficiency ?
    ### Response:
    X-linked creatine deficiency is an inherited disorder that primarily affects the brain. People with this disorder have intellectual disability, which can range from mild to severe, and delayed speech development. Some affected individuals develop behavioral disorders such as attention deficit hyperactivity disorder or autistic behaviors that affect communication and social interaction.
    