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Genetic and Rare Diseases Information Center (GARD)

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Myotonic dystrophy type 1

Other Names for this Disease
  • DM1
  • Dystrophia myotonica type 1
  • Steinert disease
  • Steinert myotonic dystrophy
  • Steinert's disease
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What is myotonic dystrophy type 1?

How is myotonic dystrophy type 1 inherited?

What is myotonic dystrophy type 1?

Myotonic dystrophy type 1, one of the two types of myotonic dystrophy, is an inherited type of muscular dystrophy that affects the muscles and other body systems (e.g., heart, eyes, pancreas).[1]  Myotonic dystrophy type 1 has been categorized into three somewhat overlapping subtypes: mild, classic, and congenital (present at birth). Symptoms of the mild form are the least severe with a normal life span. The classic form is characterized by muscle weakness and wasting, prolonged muscle tensing (myotonia), cataract, and often abnormal heart function; adults may become physically disabled and may have a shortened life span. The congenital form is characterized by severe generalized weakeness at birth (hypotonia), often causing complications with breathing and early death. The condition is inherited in an autosomal dominant pattern and is caused by mutations in the DMPK gene. [2]
Last updated: 5/11/2011

How is myotonic dystrophy type 1 inherited?

Myotonic dystrophy type 1 is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. In most cases, an affected person has one affected parent. [2]

As myotonic dystrophy is passed from one generation to the next, the disorder generally begins earlier in life and signs and symptoms become more severe. This phenomenon is called anticipation

Some individuals diagnosed with Myotonic dystrophy type 1 have an obviously affected parent; others do not. A parent may appear to be unaffected because symptoms may be mild or absent. Genetic testing is available to confirm the presence of the condition. [2]
Last updated: 5/11/2011

  1. Myotonic Dystrophy. Genetics Home Reference. November 2010; Accessed 2/16/2011.
  2. Bird, T. Myotonic Dystrophy Type 1. GeneReviews. February 8, 2011; Accessed 5/11/2011.