Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Zellweger spectrum disorder ?
    ### Response:
    Zellweger spectrum disorder is a group of conditions that have overlapping signs and symptoms and affect many parts of the body. This group of conditions includes Zellweger syndrome, neonatal adrenoleukodystrophy (NALD), and infantile Refsum disease. These conditions were once thought to be distinct disorders but are now considered to be part of the same condition spectrum.
    