Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Zellweger Syndrome ?
    ### Response:
    Zellweger syndrome is one of a group of four related diseases called peroxisome biogenesis disorders (PBD). The diseases are caused by defects in any one of 13 genes, termed PEX genes, required for the normal formation and function of peroxisomes. The PBDs are divided into two groups: Zellweger spectrum disorders and Rhizomelic Chondrodysplasia Punctua spectrum.
    