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Congenital Disorders of Glycosylation (CDG)

Comprehensive Screening Assay




March 2013

What are Congenital Disorders of Glycosylation?

Congenital disorders of glycosylation (CDG) are a group of more than 45 inherited conditions affecting several steps in the glycosylation of proteins. CDG can present with a broad clinical spectrum from developmental delay to multiorgan involvement (eg, liver disease, developmental delay, failure to thrive, chronic diarrhea, abnormal subcutaneous fat distribution, retinitis pigmentosa, cutis laxa, etc.).

CDG Sample Profiles

Sample Profiles with
Glycan Structure Analysis

CDG are classified into 2 groups:

  • Type I CDG - Characterized by defects in the assembly or transfer of the dolichol-linked glycan
  • Type II - Involves glycan processing defects

A third type- SLC35A2- was recently recognized with new genetic defects.

Cost-effective Screening Using Structural Analysis

Transferrin and apolipoprotein CIII are abundant and highly glycosylated serum proteins. Abnormal transferrin or apolipoprotein CIII isoforms are typically observed in Type I and Type II CDG, respectively. Accordingly, structural analysis of these proteins in serum provides a fast and cost-effective screening test for CDGs and is indicated for the evaluation of patients with developmental delay, failure to thrive, unexplained liver dysfunction, stroke-like episodes, seizures and muscle hypotonia, regardless of the patient’s age. The absence of the classical findings of abnormal fat deposit and inverted nipples does not exclude CDG.

Featured Test

 

Confirmed Cases of CDG Identified by Mayo Clinic Biochemical Genetics Laboratory (N=137)

Confirmed Cases of CDG Identified by Mayo Clinic Biochemical Genetics Laboratory

References

  1. He M, Matern D, Raymond K, Wolfe L: The congenital disorders of glycosylation. In Laboratory Diagnosis of Inherited Metabolic Diseases.Edited byU Garg, LD Smith, BA Heese BA. Washington, DC. AACC Press, 2012; pp 177-195
  2. Jaeken J, Matthijs G: Congenital disorders of glycosylation: a rapidly expanding disease family. Annu Rev Genomics Hum Genet 2007;8:261-278
  3. Patterson MC: Screening for "prelysosomal disorders": carbohydrate-deficient glycoprotein syndromes. J Child Neurol 1999;14(Suppl 1):S16-S22
  4. Raymond K, Grycki E, Minich S: Clinical testing for congenital disorders of glycosylation (CDG): The Mayo Clinic experience. J Inherit Metab Dis 2010;33(Suppl. 1):S74
  5. Theodore M, Morava E: Congenital disorders of glycosylation: sweet news. Curr Opin Pediatr 2011 Dec;23(6):581-587

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