Myotonic dystrophy type 2
- Dystrophia myotonica type 2
- Proximal myotonic myopathy
- Myotonic myopathy, proximal
Your QuestionMy husband has been diagnosed with type 2 myotonic dystrophy. We have two daughters who will be tested. Where can we learn more about this condition?
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Questions on this page
- What is myotonic dystrophy type 2?
- What are the signs and symptoms of myotonic dystrophy type 2?
- What causes myotonic dystrophy type 2?
- How is myotonic dystrophy type 2 inherited?
- How is myotonic dystrophy type 2 diagnosed?
- How might myotonic dystrophy type 2 be treated?
- Who can I contact to learn more about type 2 myotonic dystrophy?
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.
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.
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."
- Ankle-foot braces, wheelchairs, or other assistive devices may be used as needed for weakness
- Defibrillator placement may be needed for arrhythmias
- Cataracts can be removed for those with impaired vision
- Testosterone replacement therapy may be useful for hypogonadism in males
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.
You can also contact NINDS directly for information on type 2 myotonic dystrophy.
NIH Neurological Institute
PO Box 5801
Bethesda, MD 20824
Toll free: 800-352-9424
Web site: http://www.ninds.nih.gov/
The Muscular Dystrophy Association (MDA) provides medical services for its members through MDA clinics across the country. These clinics serve people with a range of neuromuscular disorders, including type 2 myotonic dystrophy. Patients can receive medical care at a discounted cost for genetic disorders through the MDA clinics. To learn about accessing these services, contact the MDA.
Muscular Dystrophy Association (MDA) - USA
3300 E. Sunrise Drive
Tucson, AZ 85718
Web site: http://www.mdausa.org
MDA pages on type 2 myotonic dystrophy:
International Myotonic Dystrophy Organization
PO Box 1121
Sunland, CA 91041-1121
Toll-free: (866) 679-7954 (in the USA and Canada)
Phone: (818) 951-2311
- Dalton JC, Ranum LPW, Day JW. Myotonic Dystrophy Type 2. GeneReviews. April 23, 2007; http://www.ncbi.nlm.nih.gov/books/NBK1466/. Accessed 4/8/2012.
- Learning About Myotonic Dystrophy. National Human Genome Research Institute (NHGRI). June 4, 2012; http://www.genome.gov/25521207. Accessed 4/22/2015.
- Myotonic dystrophy. Genetics Home Reference (GHR). November 2010; http://ghr.nlm.nih.gov/condition=myotonicdystrophy. Accessed 5/11/2011.
- Joline C Dalton, Laura PW Ranum, and John W Day. Myotonic Dystrophy Type 2. GeneReviews. July 3, 2013; http://www.ncbi.nlm.nih.gov/books/NBK1466/. Accessed 2/10/2014.