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Dm1 vs dm24/2/2023 ![]() The most typical appearance of DM1 is the “adult-onset” or “classic” phenotype with a CTG-repeat size ranging from 50 to 45% of patients with adult phenotype) and DM2 (40–55% of patients) ( 26, 32). Furthermore, the repeat instability leads notably to premature aging of almost all organs, so DM1 may be counted among the progeroid diseases ( 27). This results in the so called anticipation, a clinical term describing an earlier onset with a more severe phenotype in the next generations ( 26). the most severe “congenital form” with usually >1,000 CTG-repeats.ĬTG-repeats will expand in every following generation, and fully penetrant alleles occur with >50 CTG-repeats.a childhood/juvenile phenotype with early-onset and typically >800 CTG-repeats, and.a classic phenotype with a wide span from mild to severe symptoms and an expansion of 50–1,000 CTG-repeats,.a mild phenotype with an expansion of 50–150 CTG-repeats,.It is important that phenotypes and CTG-repeat sizes do not show a linear and strict relationship and thus may overlap ( 25, 26): The following four phenotypes are based on CTG-repeat sizes and onset of symtoms. An expansion between 38 and 49 repeats does typically not cause any symptoms and reflects the premutation phenotype ( 3). 5 to 37 CTG-repeats are physiologic in healthy individuals. This article is part of a Special Issue entitled “Beyond Borders: Myotonic Dystrophies-A European Perception.”įor DM1, there is a rough correlation between the expansion of CTG-repeats and the onset of symptoms as well as the severity of the disease nevertheless predictions about the clinical features and the progression of the disease based on CTG-repeat size should be made very carefully ( 23, 24). Particular attention will be given to signs and symptoms of muscular involvement, to issues related to respiratory impairment, and to the multiorgan involvement. This article highlights the clinical core features of myotonic dystrophies, thus facilitating their early recognition and diagnosis. For both subtypes, many symptoms overlap, but some differences allow their clinical distinction. Clinically, these multisystemic disorders are characterized by a high variability of muscular and extramuscular symptoms, often causing a delay in diagnosis. They are progressive, autosomal dominant diseases caused by an abnormal expansion of an unstable nucleotide repeat located in the non-coding region of their respective genes DMPK for DM1 and CNBP in DM2. ![]() Myotonic dystrophy type 1 (DM1) and type 2 (DM2) represent the most frequent multisystemic muscular dystrophies in adulthood. Friedrich-Baur-Institute, Klinikum der Universität München, Munich, Germany.
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