Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) D-bifunctional protein deficiency ?
    ### Response:
    D-bifunctional protein deficiency is a disorder that causes deterioration of nervous system functions (neurodegeneration) beginning in infancy. Newborns with D-bifunctional protein deficiency have weak muscle tone (hypotonia) and seizures. Most babies with this condition never acquire any developmental skills.
    