Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Porphyria ?
    ### Response:
    Porphyrias are rare disorders that affect mainly the skin or nervous system and may cause abdominal pain. These disorders are usually inherited, meaning they are caused by abnormalities in genes passed from parents to children. When a person has a porphyria, cells fail to change body chemicals called porphyrins and porphyrin precursors into heme, the substance that gives blood its red color.
    