Additional Information

Myotonic dystrophy type 1 (DM1) is an autosomal dominant multisystem disorder with three clinical subtypes categorized by disease severity; mild, classic, and congenital. Mild DM1 is associated with 50-150 repeats, occurs between 20-70 years of age, and is characterized by mild myotonia, cataracts, and/or diabetes mellitus. Classic DM1 is associated with 100-1000 repeats, occurs between 10-30 years, and is characterized by muscle weakness and wasting, myotonia, cataracts, cardiac conduction abnormalities, and other features. Congenital DM1 is associated with greater than 1000 repeats, with pre- and/or postnatal onset, characterized by reduced fetal movements, polyhydramnios, severe muscle weakness, hypotonia, respiratory insufficiency, and intellectual disability. Penetrance is thought to be 100% by age 50. This assay is expected to detect 100% individuals with a pathogenic variant.