Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Congenital porphyria ?
    ### Response:
    Congenital erythropoietic porphyria (CEP) is the rarest porphyria and is commonly seen in infancy, although it may begin in adulthood.  It is characterized by severe skin photosensitivity that may lead to scarring, blistering, and increased hair growth at the face and back of the hands.
    