Congenital Disorder of Glycosylation 1a : PMM2 Sequencing

Test Information

PMM2 sequencing is a molecular test used to identify variants in the gene associated with Congenital Disorder of Glycosylation 1a.

Turnaround Time

3 weeks

CPT Code(s)

81479

Cost

$1,000

Genes

Clinical Information

Congenital disorder of glycosylation (CDG) Ia is an autosomal recessive disorder caused by a deficiency of phosphomannomutase. This enzyme normally catalyzes the conversion of mannose-6-phosphate to mannose-1-phosphate. This step is required for the addition of N-linked sugars to proteins. Patients will present with hypotonia and developmental delay along with other symptoms including failure to thrive, abnormal fat distribution, seizures, stroke-like episodes and/or esotropia. Clinical presentation ranges from significantly affected infants to adolescents and adults with more minor involvement.

Indications

Molecular testing is useful to confirm the diagnosis and to identify the disease causing mutations within a family to allow for carrier testing and prenatal diagnosis.

Methodology

Sanger Sequencing

Detection

Sequencing of the gene will detect over 95% of the causative mutations in patients with CDG Ia.

Specimen Requirements

5 to 7 ml of peripheral blood collected in an EDTA (lavender top) tube is the preferred specimen type. The minimal blood needed for reliable DNA isolation is 3 ml. Extracted DNA, dried blood spots, and saliva are also accepted for this test.

Transport Instructions

The specimen should be kept at room temperature and delivered via overnight shipping. If shipment is delayed by one or two days, the specimen should be refrigerated and shipped at room temperature. Do not freeze the specimen. Samples collected on Friday can be safely designated for Monday delivery.

Prenatal Testing Information

Prenatal diagnosis is available if the familial mutations are known. Additional fees for cell culture and maternal cell contamination may apply. Maternal cell contamination studies are required for all prenatal molecular tests. Contact the laboratory prior to sending a prenatal specimen.

Have Questions Need Support?

Call our laboratory at 1-800-473-9411 or contact one of our Laboratory Genetic Counselors for assistance.
Robin Fletcher, MS, CGC
Kellie Walden, MS, CGC

Molecular Testing, Sanger Sequencing
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