Congenital disorders of glycosylation
Congenital disorders of glycosylation (CDG) have grown enormously since the discovery of the first protein glycosylation defect in 1980, presenting with a broad clinical spectrum. Expansion in number and complexity of the CDG group has even necessitated a new nomenclature. By 2011, the CDG group includes lipid glycosylation disorders and other related processes and almost 50 distinct disorders.Current research has not only expanded the spectrum of CDG types, but has also given novel insight into those previously described. The discovery of genetic defects in the conserved oligomeric Golgi complex, affecting protein glycosylation and processing through the secretory pathway, raised the concept of 'secondary' glycosylation disorders. The number of lipid glycosylation disorders, linking lipid synthesis to CDG, that were previously regarded as rare, is also increasing rapidly. In other areas of research, the bridge between muscular dystrophies and metabolic disorders is being further reinforced with the discovery of additional defects in the DPM-CDG subgroup, a CDG characterized by significant muscle involvement.It is of great importance that clinicians stay up-to-date on the field of CDG and consider it in their differential diagnosis of unknown syndromal presentations. Nevertheless, many advances have yet to be made, including information on the natural course of CDG. The lack of treatment for nearly all CDG types is striking, and the field must continue to push for innovative therapies. Clinicians and researchers must work together to describe the natural course and, most importantly, collaborate to find new therapies.