Most CDGs stem from defects in genes involved in N-linked glycosylation. Type II defects involve the processing/assembly of the of protein-bound oligosaccharide chain. There are also a series of Type I defects that involve the synthesis and transfer of the lipid-linked oligosaccharide precursor. Additional categories of CDG involve defects in O-glycosylation and defects in glycosphingolipid glycosylation. (Goreta et al., 2012, pubmed:22838182, Jaeken, 2013, pubmed:23622397).

Congenital disorders of glycosylation (CDGs) are a genetically heterogeneous group of autosomal recessive disorders caused by enzymatic defects in the synthesis and processing of asparagine (N)-linked glycans or oligosaccharides on glycoproteins. There are two main types of CDGs: type I CDGs comprise defects in the assembly of the dolichol lipid-linked oligosaccharide (LLO) chain and its transfer to the nascent protein, whereas type II CDGs refer to defects in the trimming and processing of the protein-bound glycans either late in the endoplasmic reticulum or the Golgi compartments. [from MIM:212065; 15.07.21]