Congenital Disorders of Glycosylation (CDG Ia and Ib),
Enzyme Analysis
Greenwood Genetic Center is offering clinical enzyme analysis
for phosphomannomutase (CDG Ia) and phosphomanno-isomerase (CDG Ib). Greater
than 95% of individuals with CDG Ia or Ib will have deficient enzyme levels. The
enzymes can be measure as a panel or separately.
Appropriate candidates for enzyme analysis include:
- Patients with a positive transferrin isoelectric focusing
- Patients with a strong clinical suspicion of CDG
- Patients with equivocal gene studies (a single mutation
or variants of unknown significance)
- Cases of non-immune hydrops*
- Not appropriate for carrier testing
Transferrin isoelectric
focusing, as well as mutation analysis of the
genes for CDG Ia, Ib, and Ic are also available from the biochemical laboratory.
Specimen required: Cultured fibroblasts are required
for analysis. Contact the laboratory directly (1-800-473-9411) regarding other
acceptable sample types. For cases with high clinical suspicion, DNA can also be
banked from an EDTA tube of peripheral blood for further molecular confirmation.
Transport: Please contact the laboratory before
transporting tissue for any enzyme assay. Insure that the specimen will not
freeze or get above room temperature during shipment. Fresh tissue for culture
(skin biopsy, etc.) should be sent by courier or 24-hour delivery.
Standard of Analysis: Protocol was developed by Van
Schaftingen and Jaeken (1995) and is widely used to measure these enzymes.
Time required: If cell culture is required, analysis
should be completed in 3-4 weeks. If cell culture is not required, analysis
should be available within 2 weeks of sample receipt.
Reports: Written reports with interpretation are mailed
to the referring physician. When an abnormality is detected the report will also
be telephoned to the referring physician.
CPT Codes: 82657 for single enzyme; 82657 (x2) for both
enzymes
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