disorders of glycosylation
The Congenital Disorders of Glycosylation (CDG) are a collection of over 20 inherited diseases that impair protein N-glycosylation.
The clinical appearance of CDG patients is quite diverse making it difficult for physicians to recognize them.
A simple blood test of transferrin glycosylation status signals a glycosylation abnormality, but not the specific defect.
An abnormal trasferrin glycosylation pattern suggests that the defect is in either genes that synthesize and add the precursor glycan (Glc(3)Man(9)GlcNAc(2)) to proteins (Type I) or genes that process the protein-bound N-glycans (Type II).
Type I defects create unoccupied glycosylation sites, while Type II defects give fully occupied sites with abnormally processed glycans.
These types are expected to be mutually exclusive, but a group of patients is now emerging who have variable coagulopathy and hypoglycemia together with a combination of Type I and Type II transferrin features.
Classification
congenital disorder of glycosylation type I (CDG-Is)
- congenital disorder of glycosylation type Ia (CDG-Ia)
- congenital disorder of glycosylation type Ib (CDG-Ib) (12872847)
- congenital disorder of glycosylation type II (CDG-IIs)
References
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Schulz BL, Laroy W, Callewaert N. Clinical laboratory testing in human medicine based on the detection of glycoconjugates. Curr Mol Med. 2007 Jun;7(4):397-416. PMID: 17584080
Freeze HH. Congenital Disorders of Glycosylation: CDG-I, CDG-II, and beyond. Curr Mol Med. 2007 Jun;7(4):389-96. PMID: 17584079
Freeze HH.Novel perspectives on glycosylation and human disease. Curr Mol Med. 2007 Jun;7(4):387. PMID: 17584078
Grewal PK, Hewitt JE. Glycosylation defects: a new mechanism for muscular dystrophy? Hum Mol Genet. 2003 Oct 15;12 Spec No 2:R259-64. PMID: 12925572
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