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)





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.


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.


Sanger Sequencing


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

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
Meet Makayla Gunn

Meet Makayla Gunn

Makayla was diagnosed with Rett Syndrome in April of 2015 at the age of two.   At about 18 months, we noticed she had started some repetitive hand motions, and her pediatrician was a little concerned that she did not have many words.  She had learned some sign language, and was saying ‘mama’ and ‘dada’, but that was it.  Then she suddenly stopped all of that.  At her 2 year old check-up, the pediatrician referred us to BabyNet, ...

In The News