Congenital disorders of glycosylation, dolichol and glycosylphosphatidylinositol metabolism

Numerous proteins are glycosylated with monosaccharides and/or oligosaccharide structures, also termed glycans, attached to the polypeptide chain. Most extracellular proteins, such as serum proteins, most membrane proteins and several intracellular proteins (such as lysosomal enzymes) are glycoproteins. Congenital disorders of glycosylation (CDG), first reported in 1980, are due to defects in the synthesis of glycans and in the attachment of glycans to proteins and lipids. It is a rapidly growing disease family, as the number of known CDG has increased by about 50% (from 91 to 137) in the last 5 years.