Mayo Test Catalog, (Sorted By Test Name) - Mayo Medical ...

disorders with a broad clinical spectrum including: developmental delay, hypotonia, with or without
neurological abnormalities, abnormal magnetic resonance imaging findings, skin manifestations, and
coagulopathy. There is considerable variation in the severity of this group of diseases, ranging from
hydrops fetalis to a mild presentation in adults. In some subtypes (Ib, in particular), intelligence is not
compromised. CDGs should be suspected in all patients with developmental delay, unexplained liver
dysfunction, abnormal subcutaneous fat distribution may or may not be present in all cases, stroke-like
episodes, unexplained hypoglycemia, liver disease, and with or without chronic diarrhea. The differential
diagnosis of abnormal transferrin patterns also includes liver disease not related to CDG including
uncontrolled galactosemia, hereditary fructose intolerance in acute crisis, and liver disease of unexplained
etiology. Transferrin and apolipoprotein CIII isoform analysis test is the initial screening test for CDG.
The results of the transferrin and apolipoprotein CIII isoform analysis should be correlated with the
clinical presentation to determine the most appropriate testing strategy including enzyme, molecular and
research based testing. If either CDG-Ia or CDG-Ib are suspected, it should be followed by enzymatic
analysis for phosphomannomutase and phosphomannose isomerase in leukocytes or fibroblasts
(PMMIL/PMMIF).
Useful For: Screening* test for congenital disorders of glycosylation *Positive test could be due to a
genetic or non-genetic condition. Additional confirmatory testing is required.
Interpretation: Results are reported as the mono-oligosaccharide/di-oligosaccharide transferrin
ratio. the a-oligosaccharide/di-oligosaccharide transferrin ratio, the tri-sialo/di-oligosaccharide
transferrin ratio, the apolipoprotein CIII1/apolipoprotein CIII2 ratio and the apolipoprotein
CIII0/apolipoprotein CIII2 ratio. The report will include the quantitative results and an interpretation.
The CDG profile is categorized in four types: The CDG type I profile when
mono-oligosaccharide/di-oligosaccharide transferrin ratio, and/or the
a-oligosaccharide/di-oligosaccharide transferrin ratio are abnormal. This group should have the
Apoliprotein C-III profile within the normal ranges, because in CDG type I the golgi system is not
affected. The CDG type II profile when the tri-sialo/di-oligosaccharide transferrin ratio is abnormal. In
this category the Apolipoprotein C-III profile will have two scenarios: A. the apolipoprotein
CIII1/apolipoprotein CIII2 ratio and/or the apolipoprotein CIII0/apolipoprotein CIII2 ratio will be
abnormal when the defect is most likely glycan processing in the Golgi apparatus therefore the COG
defect is likely; and B. the apolipoprotein CIII1/apolipoprotein CIII2 ratio and/or the apolipoprotein
CIII0/apolipoprotein CIII2 ratio are normal, in this cases most likely the defects do not involve the
Golgi system, thus the molecular defect is different from A. The CDG mixed type profile (Type I and II
together) in this type of profile one can have abnormal the tri-sialo/di-oligosaccharide transferrin ratio
with the mono-oligosaccharide/di-oligosaccharide transferrin ratio and/or the
a-oligosaccharide/di-oligosaccharide transferrin ratio abnormal, and may have the apolipoprotein
CIII1/apolipoprotein CIII2 ratio and the apolipoprotein CIII0/apolipoprotein CIII2 ratio normal or
abnormal, depending if the defects involve Golgi apparatus. When the profile can not be categorized
following the above classification, all the abnormal transferrin and or Apo-CIII species will be reported
descriptively according to the molecular mass stating the possible structures Reports of abnormal results
will include recommendations for additional biochemical and molecular genetic studies to more
precisely identify the correct form of CDG. Treatment options, the name and telephone number of
contacts who may provide studies at Mayo Clinic or elsewhere, and a telephone number for one of the
laboratory directors (if the referring physician has additional questions) will be provided.
Reference Values:
MONO-OLIGOSACCHARIDE/DI-OLIGOSACCHARIDE
< or =0.100
A-OLIGOSACCHARIDE/DI-OLIGOSACCHARIDE
< or =0.050
Clinical References: 1. Jaeken J, Matthijs G: Congenital disorders of glycosylation: a rapidly
expanding disease family. Annu Rev Genomics Hum Genet 2007;8:261-278 2. Freeze HH: Congenital
disorders of glycosylation: CDG-I, CDG II, and beyond. Curr Mol Med 2007;7:389-396 3. Patterson
MC: Screening for "prelysosomal disorders": carbohydrate-deficient glycoprotein syndromes. J Child
Neurol 1999;14(Suppl 1):S16-S22 4. Stibler H, Jaeken J: Carbohydrate deficient serum transferrin in a
new systemic hereditary syndrome. Arch Dis Child 1990;65:107-111 5. Freeze HH: Disorders in protein
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