Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the genetic changes related to congenital afibrinogenemia ?
    ### Response:
    Congenital afibrinogenemia results from mutations in one of three genes, FGA, FGB, or FGG. Each of these genes provides instructions for making one part (subunit) of a protein called fibrinogen. This protein is important for blood clot formation (coagulation), which is needed to stop excessive bleeding after injury.
    