Myotonic dystrophy (DM) is the most common adult muscular dystrophy. It is inherited as an autosomal dominant disorder. DM presentation ranges from congenital to adult onset. The congenital form typically presents with hypotonia and respiratory distress often followed by early death or severe mental retardation. In adults, the characteristic findings include:
- Progressive weakness
- Muscle wasting
- Lenticular opacities
- Frontal balding
- Testicular atrophy.
DM has been associated with an amplification of an unstable CTG repeat in the DMPK gene.
Testing for DM includes PCR amplification and fragment size analysis, as well as triplet-primed PCR analysis. Large size expansions may require Southern analysis for accurate size estimation.
Detection and Reference Range
Nearly all CTG expansions in the DMPK gene will be detected by this assay.
Normal individuals carry 5-34 CTG repeats. Abnormal individuals carry ≥50 repeats.
Infants and Young Children (<2 years of age): 2-3 ml
Children > 2 years of age to 10 years old: 3-5 ml
Older Children & Adults: 5-10 ml
Autopsy: 2-3 ml unclotted cord or cardiac blood
Isolation using the Perkin Elmer™Chemagen™ Chemagen™ Automated Extraction method or Qiagen™ Puregene kit for DNA extraction is recommended.
Please call the laboratory genetic counselor to arrange prenatal testing prior to collecting a prenatal sample.