Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) pyruvate dehydrogenase deficiency ?
    ### Response:
    Pyruvate dehydrogenase deficiency is characterized by the buildup of a chemical called lactic acid in the body and a variety of neurological problems. Signs and symptoms of this condition usually first appear shortly after birth, and they can vary widely among affected individuals.
    