Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the genetic changes related to Loeys-Dietz syndrome ?
    ### Response:
    The four types of Loeys-Dietz syndrome are distinguished by their genetic cause: mutations in the TGFBR1 gene cause type I, mutations in the TGFBR2 gene cause type II, mutations in the SMAD3 gene cause type III, and mutations in the TGFB2 gene cause type IV.
    