Myotonic Dystrophy 1 (DMPK) Genetic Testing (Repeat Expansion)
Use
Type 1 myotonic dystrophy results from a mutation in the DMPK gene known as a trinucleotide repeat expansion. This mutation increases in the size of the repeated CTG segment in the DMPK gene. People with type 1 myotonic dystrophy have from 50 to 5,000 CTG repeats in most cells. The number of repeats may be even greater in certain types of cells, such as muscle cells.
Special Instructions
This test is not available for patients in New York state. Careful attention should be given to the collection instructions: whole blood should be collected using standard phlebotomy, oral swabs need to follow kit instructions, and for extracted DNA, MNG Genetic Services must be contacted.
Limitations
The test may produce false positive or negative results due to factors such as rare genetic variants, allele dropout, blood transfusions, or mosaicism. There are also maximum reportable sizes for repeat expansion testing in various genes, with DMPK being reportable up to 150 repeats. Results above this range are reported as greater than the largest reportable size.
Methodology
PCR-based (Repeat-primed PCR)
Biomarkers
Result Turnaround Time
2-4 weeks
Related Documents
For more information, please review the documents below
Specimen
Whole Blood
Volume
4 mL
Minimum Volume
2 mL
Container
lavender-top (EDTA) tube
Collection Instructions
standard phlebotomy
Storage Instructions
Maintain specimen at room temperature or refrigerate at 4°C. Do not freeze.
Causes for Rejection
Frozen or hemolyzed specimen; quantity not sufficient for analysis; improper container
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 14 days |
| Refrigerated | 30 days |