Mucolipidosis II/IIIA & III gamma (GNPTAB & GNPTG) Sequencing
|Disorders||Mucolipidosis II (ML II, I-Cell disease)
Mucolipidosis III Alpha/Beta (ML IIIA, Pseudo-Hurler Polydystrophy)
Mucolipidosis III Gamma (ML III gamma, ML IIIC)
|Clinical info||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). Individuals with ML II or ML II/III have mutations in the GNPTAB gene, which has been localized to 12q23.3. ML II is associated with a more severe course, with death usually in childhood. ML II/ML III is associated with a milder course with a wider spectrum of features and severity. Both types are slow progressive disorders characterized by restricted growth, skeletal abnormalities, cardiac involvement, and respiratory problems.
Mucolipidosis III gamma more rare than ML II and IIIA. ML III gamma has a very similar presentation and progression as the other sub-types, but is caused by mutations in the GNPTG gene. Reflex sequecning of this gene is available at no additional charge when GNPTAB testing is normal.
Dr. Sara Cathey of the Greenwood Genetic Center is actively involved in research on MLII/IIIA.
|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.|
|Associated Tests||Mucolipidosis II/III (Plasma Screen)|
|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 10 ml of peripheral blood collected in an EDTA (lavender top) Vacutainer tube is preferred. The minimal blood needed for reliable DNA isolation is 3 ml|
|Transport||The specimen should be kept at room temperature and delivered via overnight shipping. FedEx is preferred. 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.|
|Turnaround time||6 weeks|
|Prenatal testing||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.|
|CPT Codes||GNPTAB - Unknown mutation
GNPTG - Unknown mutation *only if ordered as separate test - no charge if reflexed after GNPTAB*
$2000 for GNPTAB sequencing
Molecular Diagnostic Lab
The Molecular Diagnostic Lab offers DNA analysis for many genetic disorders via gene sequencing, targeted mutation analysis, MLPA deletion/duplication testing, trinucleotide repeat analysis and next generation sequencing panels.