Congenital disorders of glycosylation(CDG) are a rapidly growing group of genetic diseases that are due to defects in the synthesis of glycans and in the attachment of glycans to other compounds. Most CDG are multisystemic diseases often involving severe psychomotor retardation. The CDG causing sialic acid deficiency of N-glycans can be diagnosed by isoelectric focusing of serum transferrin. Glycan structural analysis, yeast genetics and knockout animal models are essential tools in the elucidation of novel CDG. In this review, we focus on the current knowledge of the pathogenesis and identification of nine primary glycosylation diseases.
