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Don’t fight Myotonic dystrophy type 1 alone.
Find your community on the free RareGuru App.Myotonic dystrophy* type 1 (MD1), * 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, endocrine system, and central nervous system). MD1 has three forms that somewhat overlap: the mild form, classic form, and congenital form (present at birth). The mild form has the least severe symptoms of the different forms of MD1 and is associated 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 with the classic form may become physically disabled and may have a shortened life span. The congenital form is characterized by severe generalized weakness at birth (hypotonia), often causing complications with breathing and early death. MD1 is inherited in an autosomal dominant manner and is caused by mutations in the DMPK gene. Treatment is based on the signs and symptoms present.
Source: GARD Last updated on 05-01-20
People with MD1 have progressive muscle wasting and weakness beginning in their 20's or 30's. The muscle wasting and weakness develop in their lower legs, hands, neck and face. They also have stiffness and tightness of their muscles (called myotonia), so they are slow to relax certain muscles after using them. This condition is characterized by difficulty releasing the hand from a handshake or a doorknob. In addition to muscle weakness and wasting, people who have MD1 may have fatigue, muscle pain, difficulty swallowing, clouding of the lens in their eyes (cataracts), and irregularities in the electrical control of their heartbeat (cardiac conduction defects). People with advanced disease may develop respiratory complications. Men with MD1 have changes in their hormones that can cause balding and sometimes the inability to father a child (infertility). The severity of symptoms varies among people with MD1.
Compared to myotonic dystrophy type 2, MD1 is more severe and may affect lifespan.
Last updated on 05-01-20
MD1 is caused by a mutation called a CTG trinucleotide repeat in the DMPK gene. It is made up of three DNA building blocks (CTG stands for cytosine, thymine, and guanine) that appear multiple times in a row. If the number of CTG repeats is more than 34, it creates an unstable region in the gene. Repeats between 35 and 49 are considered premutations. Individuals with CTG repeats in this range do not have symptoms themselves, but their children are at increased risk of inheriting a larger repeat size and thus having symptoms.
The protein made by the DMPK gene is believed to play a role in communication and impulse transmission within and between cells. It appears to be important for the correct functioning of cells in the heart, brain, and skeletal muscles. The more than normal number of CTG repeats leads to the creation of longer and toxic RNA. This causes problems for cells mainly because it traps and disables important proteins. This prevents cells in muscles and other tissues from functioning normally, leading to the signs and symptoms of MD1.
Last updated on 05-01-20
MD1 is inherited in an autosomal dominant pattern, which means one copy of the mutated gene in each cell is sufficient to cause the disorder. In most cases, the person with MD1 has a parent who also has the disorder. The children of a person with MD1 have a 50% chance of inheriting the disorder.
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. It is caused by an increase in the length of the number of CTG repeats (unstable region) in the DMPK gene. The expansion of the unstable region causes the features of the disorder to become more severe with each successive generation.
Some people diagnosed with MD1 have a parent who has the signs and symptoms of the disorder; 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.
Last updated on 05-01-20
Yes. Sleepiness and fatigue are common features of myotonic dystrophy type 1. Medications to reduce fatigue are available. We recommend that you dicuss your treatment options with a healthcare provider.
In addition, heart block is a common and potentially dangerous complication of myotonic dystrophy type 1, that can cause light headedness, dizzy spells, near fainting, and fainting. These symptoms should be reported to your doctor right away.
Last updated on 05-01-20
Treatment of eye and vision problems must be individually tailored. Refractive error and astigmatism can be corrected with eyeglasses, contact lenses, or surgery. Special glasses with eye "crutches" can be used to improve vision in people with ptosis. Surgery can be done to treat ptosis and cataracts, however ptosis often recurs and special precautions must be taken with anesthesia. If severe, strabismus may also be treated with surgery.
Last updated on 05-01-20
Myotonic dystrophy type 1 is associated with an increased risk for a variety of vision and eye problems, including:
Last updated on 05-01-20
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