Myotonic Dystrophy

What is Myotonic Dystrophy?

It is a rare inherited disorder belonging to a group of disorders known as muscular dystrophies. Myoptic Dystrophy is the most common form of muscular dystrophy and it usually starts in adulthood. Features of the syndrome include muscle wasting and weakness as well as myotonia (prolonged muscle contractions) which makes it difficult for affected individuals to release their muscles after using them. There are two main types of the disorder.

It affects 1 in every 8,000 people worldwide.

What gene changes cause Myotonic Dystrophy?

  • Type 1 of the syndrome is caused by changes in the DMPK gene.
  • Type 2 of the syndrome is caused by changes in the CNBP gene.

The syndrome is inherited in an autosomal dominant pattern.

As the disorder is inherited from generation to generation, with each inheritance it presents with symptoms earlier in life and a severe form in a process known as anticipation. This is only relevant to type 1 of the syndrome.

What are the main symptoms of Myotonic Dystrophy?

The syndrome’s main symptoms include muscle wasting and weakness that progresses and worsens with age. Muscle contractions or myotonia are also common.


Type 1 of the syndrome is a more severe form of the disorder. Type 2 is generally recognized to be a milder form. The main difference in the syndromes between the two types is the muscles affected.

In Type 1 symptoms tend to affect the distal or outer muscles in the lower legs, hands, neck, and face. In Type 2 muscle weakness affects mainly the proximal bodies, or those closer to the center of the body such as the neck, shoulders, elbows and the hips. This difference in symptoms is due to the different gene mutations that cause each type.


Within Type 1 of the syndrome, there are a further two forms of the syndrome- mild and congenital. The mild form tends to present later in life around mid adulthood and symptoms include mild myotonia and cataracts. The congenital form presents at birth with low muscle tone, clubfoot, respiratory issues as well as intellectual disability and delayed development. These health issues tend to cause more serious and sometimes life threatening issues.

How is it diagnosed?

To find out if someone has a diagnosis of Myotonic Dystrophy, it is important to have a consultation and evaluation with a clinical genetic specialist.  Specialists may also suggest specific genetic testing or other types of tests to help reach a diagnosis.  FDNA’s AI technology can help speed up the diagnostic process by analyzing facial features and other health information.

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