Myotonic dystrophy type 1

Last revised by Laura Meeker on 8 Apr 2022

Myotonic dystrophy type 1, also known as Steinert disease, is a rare autosomal dominant multisystem disorder.

In adults, it is mainly characterized by muscle weakness, myotonia, cardiac conduction defect and posterior subcapsular cataracts 1. In neonates, it is characterized by hypotonia and respiratory distress often leading to death 1.

The disease has a variable onset as it can be seen in adults (adult-onset) and children (congenital form). The diagnosis is established with genetic testing.

Myotonic dystrophy type 1 is caused by a CTG trinucleotide repeat expansion in the DMPK gene on chromosome 19. Increased number of repeats correlates with increased severity and earlier onset of the disease 1.

MRI features are nonspecific and include bilateral supratentorial white matter lesions and mild cortical atrophy 2. Subcortical white matter lesions most commonly involve the frontal lobes but can also be seen in the temporo-insular region. The latter feature is not seen with myotonic dystrophy type 2 2,3.

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