Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the genetic changes related to thrombotic thrombocytopenic purpura ?
    ### Response:
    Mutations in the ADAMTS13 gene cause the familial form of thrombotic thrombocytopenic purpura. The ADAMTS13 gene provides instructions for making an enzyme that is involved in the normal process of blood clotting. Mutations in this gene lead to a severe reduction in the activity of this enzyme.
    