Although classified as a muscular dystrophy, myotonic dystrophy (DM) is a multisystem disease inherited as an autosomal dominant trait. There are at least two forms, with core features of myotonia, muscular dystrophy, cardiac conduction defects, endocrine abnormalities, and iridescent cataracts. DM type 1 (DM1) is caused by an expansion of cytosine thymine guanine (CTG) repeat located in the 3' untranslated region of DM protein kinase (DMPK) on chromosome 19q13.3. DM type 2 (DM2), also known as proximal myotonic myopathy (PROMM), is a milder and less common condition and results from an unstable CCTG repeat in intron 1 of zinc finger protein 9 (ZNF9) on chromosome 3q31. In addition to palliative measures, prevention of sudden death due to cardiac arrhythmia is crucial in patients with DM. Several experimental approaches directed against expanded repeat ribonucleic acid (RNA) using RNA interference tools, antisense oligonucleotides, and oligomers may provide future treatment options.
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