History
The first CDG patients (twin sisters) were described in an abstract in the medical journal Pediatric Research in 1980 by Jaeken et al. Their main features were psychomotor retardation, cerebral and cerebellar atrophy and fluctuating hormone levels (e.g.prolactin, FSH and GH). During the next 15 years the underlying defect remained unknown but since the plasmaprotein transferrin was underglycosylated (as shown by e.g. isoelectric focusing), the new syndrome was named carbohydrate-deficient glycoprotein syndrome (CDGS). Its "classical" phenotype included psychomotor retardation, ataxia, strabismus, anomalies (fat pads and inverted nipples) and coagulopathy.
In 1994, a new phenotype was described and named CDGS-II. In 1995, Van Schaftingen and Jaeken showed that CDGS-I (now CDG-Ia or PMM2-CDG) was caused by the deficiency of the enzyme phosphomannomutase. This enzyme is responsible for the interconversion of mannose-6-phosphate and mannose-1-phosphate, and its deficiency leads to a shortage in GDP-mannose and dolichol (Dol)-mannose (Man), two donors required for the synthesis of the lipid-linked oligosaccharide precursor of N-linked glycosylation.
In 1998, Niehues et al. published a new CDG syndrome, CDG-Ib, which is caused by mutations in the enzyme metabolically upstream of PMM2, phosphomannose isomerase (PMI). In this paper, the authors also described a functional therapy for CDG-Ib, alimentary mannose.
The characterization of new defects took up speed and several new Type I and Type II defects were delineated.
Read more about this topic: Congenital Disorder Of Glycosylation
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