Myotonic dystrophy type 1

Myotonic dystrophy type 1 (DM1) is a distal myopathy and a multisystem disease occurring with an incidence of 1/8000, as a result of a CTG trinucleotide repeat expansion in the serinetreonine-protein kinase (DMPK) coding gene on chromosome 19q13.3. In DM1 patients the length of the CTG expansion ranges from 50 to 4000. Disease severity correlates with repeat length and the phenomenon of genetic anticipation is frequent. DMPK mRNA disturbs splicing of pre-mRNA of a vast number of other genes coding for chloride channels, insulin receptor, muscle and cardiac troponine T, tau protein etc, resulting in a multisystem character of the disease. DM1 patients often exhibit cataracts (>80%), cardiac disturbances (up to 90%), respiratory failure, central and peripheral nervous system dysfunction, endocrine and other disturbances. These patients often present with apathy, hypersomnia, dysexecutive syndrome, visuo-spatial deficit and attention disturbances. Brain MRI in DM1 patients frequently demonstrates diffuse white matter hyperintense lesions, while voxel-based morphometry shows marked reduction of both white and grey matter.