Myotonic dystrophy type 2

What causes myotonic dystrophy type 2?

Mutations in the CNBP gene cause myotonic dystrophy type 2. The exact function of this gene is not known. The protein made by the CNBP gene is mainly found in the heart and in skeletal muscles, where it probably helps regulate the function of other genes.

In people with myotonic dystrophy type 2, a short piece of DNA is abnormally repeated many times, forming an unstable area of the gene. The mutated gene makes an altered version of messenger RNA (mRNA), which is a copy of the gene that is normally used for protein production. The abnormal mRNA forms clumps inside the cell that interfere with the production of many proteins. These changes prevent cells in muscles and other tissues from functioning normally, leading to the signs and symptoms of myotonic dystrophy.

Last updated on 05-01-20

How is myotonic dystrophy type 2 diagnosed?

Myotonic dystrophy is diagnosed by doing a physical exam. A physical exam can identify the typical pattern of muscle wasting and weakness and the presence of myotonia. A person with myotonic dystrophy may have a characteristic facial appearance of wasting and weakness of the jaw and neck muscles. Men may have frontal balding.

There are several laboratory tests that can be used to clarify the clinical diagnosis of myotonic dystrophy. One test, called electromyography (EMG), involves inserting a small needle into the muscle. The electrical activity of the muscle is studied and usually shows characteristic patterns of muscle electrical discharge. The definitive test for myotonic dystrophy type 2 is a genetic test. For this test, certain cells within the blood are analyzed to identify a change (mutation) in the CNBP gene.

The University of Washington provides more information on genetic testing for myotonic dystrophy type 2 in their publication titled, "Myotonic Dystrophy: Making an Informed Choice About Genetic Testing."

Last updated on 05-01-20

How is myotonic dystrophy type 2 inherited?

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

As myotonic dystrophy is passed from one generation to the next, it generally begins earlier in life and signs and symptoms become more severe. This phenomenon is called anticipation. The cause of the anticipation in families with myotonic dystrophy type 2 is unknown.

Last updated on 05-01-20

What is the long-term outlook for people with myotonic dystrophy type 2?

In general, people with myotonic dystrophy type 2 have a better long-term outlook (prognosis) than those with type 1. Symptoms are usually relatively mild. While the rate of progression can vary among affected people, symptoms generally progress slowly. While mobility may be impaired at an earlier age, the ability to walk is often retained until around 60 years of age.

The prognosis for affected people can depend on the extent of heart (cardiac) involvement. While definitive information is not available, it appears there is relatively little shortening of the lifespan in people with myotonic dystrophy type 2.

Last updated on 05-01-20

How might myotonic dystrophy type 2 be treated?

There is currently no treatment available to stop or slow the progression of myotonic dystrophy type 2. Management options depend on the symptoms that each affected person has, and aim to treat each specific symptom. For example:

Myotonia is usually mild and rarely requires treatment. Routine exercise appears to help with pain control, as well as with muscle strength and endurance. The effectiveness of most medications for pain management varies. Mexilitene, which is very effective for some forms of myotonia, has helped control muscle pain in some people with this condition. Other medications that have been used with some success include gabapentin, nonsteroidal anti-inflammatory drugs (NSAIDS), low-dose thyroid replacement, low-dose steroids, and tricyclic antidepressants. Cholesterol-lowering medications should be avoided when they are associated with increased weakness.

There are steps a person can take to prevent some secondary complications. Anesthetic risk may be increased, so careful assessment of heart and respiratory function before and after surgery are recommended. Affected people should also have a yearly electrocardiogram or cardiac MRI to detect possible conduction defects or cardiomyopathy.

You can see more detailed information about the management of myotonic dystrophy type 2 on the GeneReviews Web site.

Last updated on 05-01-20

Where To Start

Myotonic Dystrophy Foundation

Myotonic Dystrophy Foundation provides additional information about Myotonic dystrophy type 2.

Last updated on 04-27-20

Myotonic dystrophy

The Muscular Dystrophy Association (MDA) provides additional information about myotonic dystrophy. Click on the link to view this information.

Last updated on 04-27-20

Name: Myotonic Dystrophy Foundation 1004-A O'Reilly Avenue
San Francisco, CA, 94129, United States
Phone: +1-415-800-7777 Toll Free: 1-86-MYOTONIC (1-866-968-6642) Email: info@myotonic.org Url: https://www.myotonic.org
Name: Muscular Dystrophy Association MDA 222 S Riverside Plaza Suite 1500
Chicago, IL, 60606, United States
Toll Free: 1-833-275-6321 (Helpline) Email: resourcecenter@mdausa.org Url: https://www.mda.org
Name: Muscular Dystrophy UK 61A Great Suffolk Street
London, SE1 0BU, United Kingdom
Phone: (+44) 0 020 7803 4800 Toll Free: 0800 652 6352 (Helpline) Email: info@musculardystrophyuk.org Url: https://www.musculardystrophyuk.org/
Name: Myotonic Dystrophy Support Group 19-21 Main Road Gedling
Nottingham NG4 3HQ
United Kingdom
Phone: 0808 169 1960 Email: contact@mdsguk.org Url: http://www.myotonicdystrophysupportgroup.org/

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