Congenital disorders of glycosylation (CDGs) are a group of autosomal recessive disorders caused by enzymatic defects in the synthesis and processing of asparagine (N)-linked glycans or oligosaccharides on glycoproteins. These glycoconjugates play critical roles in processes such as metabolism, cell recognition and adhesion, cell migration, protease resistance, host defense, and antigenicity. CDGs are divided into 2 main groups: 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 comprise defects in the trimming and processing of protein-bound glycans (Marquardt & Denecke 2003, Grunewald et al. 2002, Hennet 2012, Cylwik et al. 2013).