Mucolipidosis III Gamma : GNPTG Sequencing

Test Information

GNPTG sequencing is a molecular test used to identify variants in the gene associated with Mucolipidosis III Gamma .

Turnaround Time

6 weeks

CPT Code(s)

81479

Cost

$1,000

Genes

Clinical Information

Mucolipidosis II (ML II), also known as I-Cell disease, and Mucolipidosis IIIA (ML IIIA), also known as Pseudo-Hurler Polydystrophy, are lysosomal storage disorders caused by a deficiency of N-acetylglucosamine-1-phosphotransferase (NAPT). ML II is associated with a more severe course including growth failure and failure to thrive, severe developmental delay, coarse facial features, skeletal anomalies and frequent upper respiratory infections. ML II is often lethal in childhood. ML IIIA is associated with a similar, but milder course with a wider spectrum of features and severity. In ML II and ML IIIA, lysosomal hydrolase enzymes are not properly targeted to the lysosome. Therefore, the enzyme activity of multiple lysosomal hydrolases is increased in plasma and other body fluids.

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 mutations in >95% of individuals with MLII/IIIA. GNPTG sequencing can be requested separately or reflexed if GNPTAB sequencing is normal.

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
Lucy's Story

Lucy's Story

When our daughter Lucy had a metabolic crisis at 7 days old, we were shocked and devastated to find out that she was born with a rare genetic disorder (MSUD). Her newborn screening results did not make it back in time to prevent the crisis, and no one at our local hospital was familiar with the disease. They did not know how to treat her. Calls were made to Greenwood Genetic Center to confirm her diagnosis...

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