What is Myotonic Dystrophy?

About DM

  Myotonic dystrophy is a very complicated condition. The symptoms and disease progression can vary widely. The effects can be quite different even among members of the same family, so it is difficult to predict just how the disorder will affect you and your family. One person may only have mild muscle pain or cataracts that develop in later years, while someone else with the condition may be born with serious breathing problems.The most common effects of DM are muscle problems, including muscle weakness (myopathy), trouble relaxing a muscle (myotonia), and muscle wasting that gets worse over time (atrophy). However, it is misleading to think of DM as only a muscle disorder because it also affects many other body functions, including the heart, lungs, and gastrointestinal (GI) system. The disorder can also cause problems with cognitive function, personality, and vision. Not everyone with DM will have all or even most of the possible symptoms. 

Disease Mechanism

 Myotonic dystrophy is one of the most complex disorders known. In addition to the incredible variability of clinical symptoms the disease also has unique mechanistic features:

  • True autosomal inheritance. The disease phenotype of patients who are homozygous for myotonic dystrophy is essentially the same as those who are heterozygous.
  • Variable penetrance. Considerable variability is seen between affected individuals, even within the same family. Somatic mosaicism is common, where the genetic defect can be significantly different in various tissues in a single individual and can change over time.
  • Anticipation. The disease symptoms tend to be more severe and occur earlier in successive generations.
  • Maternal transmission bias for the congenital form. In the most severe form of myotonic dystrophy (congenital myotonic dystrophy: DM1), transmission is nearly always maternal and does not appear to be related to the severity of the disease in the mother. The mutated gene is only very rarely inherited from the father in newborns with myotonic dystrophy.


Thanks to you - the MDF community members who volunteer, donate, advocate and help fulfill our Care and a Cure mission - MDF has become the world’s largest DM-only patient advocacy organization, serving individuals and families around the world.Every day, we focus on helping families living with myotonic dystrophy by delivering comprehensive support resources, and driving research to accelerate the discovery of DM therapies. You make this work possible, and we want you to know just how much impact you have helped to create. We created a short overview of our recent efforts and impact for your review. Click on the icons below to view the MDF "Our Impact" statement, the MDF Care Programs Report and our audited financial statements. 

Community Voices

Hope & Inspiration


About This Page

All the information including the Video are from the MDF www.myotonic.org.