Myotonic Dystrophy

Disorder Myotonic dystrophy, DM1
Gene Name DMPK
Clinical info Myotonic dystrophy is the most common form of adult onset muscular dystrophy and has an incidence of 1/8000 individuals. The genetic defect in the disorder is the expansion of a (CTG) trinucleotide repeat in the DMPK gene. This autosomal dominant disorder is characterized by myotonia, muscle wasting, frontal balding, hypogonadism, and ocular and ECG abnormalities. Genetic anticipation is commonly seen in families with myotonic dystrophy. In these families, extreme amplification can occur during mother to child transmission of the abnormal allele leading to a congenital form of the disease. Congenital myotonic dystrophy can be associated with a very severe disease state including generalized hypotonia and intellectual disability. Molecular diagnosis of myotonic dystrophy involves a combination of Southern blotting tests and direct PCR analysis to determine the (CTG) repeat number.
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.
Detection PCR and Southern blot analysis are used in combination to determine allele repeat size.  PCR will detect up to approximately 100 CTG repeats while Southern blot is used to detect the larger repeats.
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 3 weeks
Prenatal testing Prenatal diagnosis is available. 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 81401


Prenatal diagnosis is $1000.  Please contact the laboratory for more information.

Contact For further information contact one of our This email address is being protected from spambots. You need JavaScript enabled to view it. at 1-800-473-9411.

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.

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