Myotonic Dystrophy Type 1 Repeat Expansion Analysis (Prenatal Diagnosis)

Casandra

Casandra Test Code BA11886Version 1 (DRAFT)

Performing Lab

Lab Baylor GeneticsLab Test ID 6105CPT Code 81234

Myotonic Dystrophy Type 1 Repeat Expansion Analysis (Prenatal Diagnosis)

Clinical Use

Use

The Myotonic Dystrophy Type 1 Repeat Expansion Analysis determines the number of CTG repeats in the DMPK gene. Myotonic dystrophy type 1 represents the most common form of adult muscular dystrophy, with symptoms that can appear from congenital stages to adulthood. Its presentation can include hypotonia, intellectual disability, progressive weakness, and cataracts, with congenital forms often leading to severe fetal complications. Affected pregnancies may exhibit abnormal ultrasound findings. Relevant diagnostic testing or carrier screening is recommended for at-risk pregnant individuals, particularly those with a family history or concerning ultrasound results.

Special Instructions

For this test, a considerable amount of extracted DNA is necessary, so cultured amniocytes are essential for accurate DNA extraction. Baylor Genetics will grow these cultured amniocytes if samples are not provided from another laboratory, ensuring that sufficient DNA is available for testing. This process optimizes test accuracy and patient care, especially in prenatal contexts.

Limitations

This analysis may not detect all possible mutations associated with myotonic dystrophy. Additionally, it is sensitive only for repeat sizes typically between 30-80. Specimens must meet specific shipping criteria to ensure the viability of results, as failed specimens cannot be refrozen. Results depend on adequate DNA extraction, and the presence of minor repeat expansions or mutations may not be detectable by standard methods, which may limit its interpretability in certain cases.

Test Details

New York Approved