Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Congenital disorders of glycosylation ?
    ### Response:
    Congenital disorders of glycosylation (CDG) are a group of inherited metabolic disorders that affect a process called glycosylation. Glycosylation is the complex process by which all human cells build long sugar chains that are attached to proteins, which are called glycoproteins.
    