Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) porphyria ?
    ### Response:
    Porphyria is a group of disorders caused by abnormalities in the chemical steps that lead to heme production. Heme is a vital molecule for all of the body's organs, although it is most abundant in the blood, bone marrow, and liver. Heme is a component of several iron-containing proteins called hemoproteins, including hemoglobin (the protein that carries oxygen in the blood).
    