Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) citrullinemia ?
    ### Response:
    Citrullinemia is an inherited disorder that causes ammonia and other toxic substances to accumulate in the blood. Two forms of citrullinemia have been described; they have different signs and symptoms and are caused by mutations in different genes.  Type I citrullinemia (also known as classic citrullinemia) usually becomes evident in the first few days of life.
    