Myotubular Myopathy, X-linked : MTM1 Sequencing

Test Information

MTM1 sequencing is a molecular test used to identify variants in the gene associated with X-linked Myotubular Myopathy.

Turnaround Time

6 weeks

CPT Code(s)

81406

Cost

$1,500

Genes

  • MTM1

Clinical Information

This X-linked disorder primarily affects males with female carriers usually being asymptomatic. Respiratory distress, hypotonia , and muscle weakness are common manifestations in the newborn period for all three forms of the disorder (mild, moderate and severe). The severe form can present prenatally with polyhydramnios and decreased fetal movement; these patients may require a ventilator permanently. Motor milestones can range from mildly delayed to significantly delayed with some patients never being able to ambulate. The muscle weakness can also involve the facial and extraocular muscles. Mildly affected patients may only need ventilator support in the neonatal period and achieve ambulation.

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 MTM1 gene will detect a mutation in a majority of patients. It is estimated that about 7% may have a deletion or duplication.

Specimen Requirements

The preferred sample type is peripheral blood collected in an EDTA (purple top) tube - at least 2-3ml for pediatric patients and 5-6ml for adult patients. Extracted DNA, dried blood spots, and saliva are also accepted for this test. Saliva samples must be submitted in an approved saliva kit. Contact the lab to receive a saliva kit or to have one sent to your patient.

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
Falecia Thomas, MS, CGC

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