Myotonic Dystrophy Type 1

Myotonic dystrophy type 1 (DM1) is a genetic disorder that affects muscles and other systems of the body, causing progressive muscle weakness and prolonged muscle contractions (myotonia). DM1 is a multisystem condition requiring lifelong, multidisciplinary care. Life expectancy can be shortened, especially in severe or congenital cases.

  • Cause: Caused by a CTG repeat expansion in the DMPK gene on chromosome 19. It is inherited in an autosomal dominant pattern, and the number of repeats often increases in successive generations (genetic anticipation), leading to more severe symptoms.

  • Features: Muscle weakness and wasting (especially face, neck, and lower legs), myotonia (delayed muscle relaxation), cataracts, daytime sleepiness, cardiac conduction defects, endocrine issues (e.g., insulin resistance, infertility), and cognitive or learning difficulties. Severity and age of onset vary.

  • Diagnosis: Confirmed by genetic testing to detect the CTG repeat expansion.

  • Treatment: No cure. Management includes physical therapy, medications for myotonia, cardiac monitoring, and treatment of associated conditions (e.g., sleep disorders, endocrine problems).

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