Myotonic Dystrophy

Updated May 24, 2019

This article was scientifically reviewed by YourDNA

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A list of references is also included at the bottom of this article.

It’s scary having a diagnosis in the family of a rare disease. It’s something that completely changes your everyday life and can greatly impact your future. At YourDNA, we understand the importance of researching the disease as much as possible. We’ve compiled information so you can understand the disease better and know what to expect.

What's in this Guide?

Disclaimer: Before You Read

It is important to know that your genes are not your destiny. There are various environmental and genetic factors working together to shape you. No matter your genetic makeup, maintain ideal blood pressure and glucose levels, avoid harmful alcohol intake, exercise regularly, get regular sleep. And for goodness sake, don't smoke.

Genetics is a quickly changing topic.

What Is Myotonic Dystrophy?

Myotonic dystrophy (DM) falls into a category of inherited disorders known as muscular dystrophies. This condition affects muscles and numerous organs in the body, often leading to muscle weakness and progressive degeneration.

This form typically begins in adulthood, typically among people who are in their 20s and 30s. It affects approximately 1 in 8,000 people all over the world 1.

Myotonic dystrophy is normally classified as a muscle disease, but this condition is also known to affect other parts of the body including the skeletal system. The condition affects people differently, even people who are in the same family, making the disease a hard one to treat and understand fully in some situations.

Since myotonic dystrophy is a progressive disease, it worsens over time. There are different types of this disease, DM1 and DM2, and both affect patients in different ways.

Patients with DM1 that have mild symptoms can generally live a normal lifespan. The prognosis for DM2 isn’t entirely clear, patients with this type can also live a normal lifespan in most cases but may end up losing their mobility at a young age.

Aside from DM1 and DM2, there’s also congenital myotonic dystrophy 2, or CDM, which occurs at birth and can lead to life-threatening complications. It is possible for infants to outgrow the muscle-related complications of the disease but will never fully be rid of them. Aside from muscles being affected at a young age, hearing and vision are often affected as well.

Individuals with myotonic dystrophy usually begin feeling weakness in their neck, face, lower legs, and hands, often also experiencing a tightness around these muscles. The tightness can make it hard for someone to relax their muscles right after using them.

Individuals who experience this might have trouble releasing their hand on a doorknob or letting go after a handshake.

Muscle weakness is just one of the many characteristics of myotonic dystrophy. Men can have a change in their hormones that can lead to the inability to father a child.

Babies born with myotonic dystrophy usually have weakness in all of their muscles and experience developmental delays, such as mental retardation.

How Is Myotonic Dystrophy Inherited?

Both types of Myotonic dystrophy are inherited if families have an autosomal dominant pattern.

This means that one copy of the mutated gene in each cell will cause this disease. Typically, if a child has Myotonic dystrophy, they have a parent with the same disorder.

Families with myotonic dystrophy pass the mutated gene from one generation to the next. The chances of a parent with Myotonic dystrophy passing the disease onto their child is relatively high, approximately 50-percent.

Mothers pass congenital myotonic dystrophy in almost all cases.

What Causes Myotonic Dystrophy?

DM1 is caused by a mutation to the DMPK gene, which plays an important role in brain cells, heart, and muscle, although the exact roles remain unclear.

DM2 results in a mutation to the CNBP gene, which is found in the skeletal muscles and heart. Even though the mutations occur on two separate genes for DM1 and DM2, they can affect various cells in the same manner, including some cells in the nerves and heart.

Diagnosis of Myotonic Dystrophy

Doctors perform a physical exam to identify the specific pattern of muscle weakness and wasting to diagnose this condition.

There are some physical characteristics that can help lead doctors to a proper diagnosis of myotonic dystrophy.

During the initial appointment, doctors will look at many things, especially a patient’s family history. They will take into account the different symptoms a person has and then proceed with a physical examination.

Men with this condition typically experience early balding in the front of their scalp, adults may also experience drooping of the eyelids, and their temples may look hollow due to their chewing muscles being affected.

Afterward, they think the patient is likely to have myotonic dystrophy, they will ask the patient to undergo a blood test so they can look for the abnormal mutation of the gene. In addition to genetic testing, there are some types of testing that can be performed to get a clinical diagnosis of the condition.

One of the tests is called electromyography, or an EMG. An EMG is performed by having a small needle inserted into the muscles to study the electrical discharge to look for specific characteristics.

The purpose of the EMG is to determine if there is any nerve dysfunction or any problems with the transmission from the nerves to the muscles.

Myotonic Dystrophy Genetics

Genetic testing, also referred to as DNA testing, is available to determine whether a person has myotonic dystrophy definitively.

For a genetic test, the doctor will need a sample of blood from the patient so they can test for the mutation. It generally takes about three weeks to receive the results of a genetic test, but the time varies depending on the laboratory.

There are many benefits to getting a genetic test to determine if you have myotonic dystrophy. One of the main ones is finally having a definitive answer so you don’t have to undergo any additional testing.

This is also a good way to help reduce stress and anxiety because you’ll know the cause of the symptoms you’re experiencing.

If someone is at risk of having myotonic dystrophy but are not displaying any of the usual symptoms, they may want to get a genetic test performed just to make sure they won’t develop the condition in the future.

Finding out if you’re at risk of developing it can help you start planning for future complications.

Knowing you have a disease does come with stress, but it can help you take time to better understand how your life will change and what you can do about it. If someone in your family has it, especially a parent, it’s wise to take a genetic test so you can know for sure, which is something that will give you peace of mind.

There are a few reasons why someone with myotonic dystrophy does not exhibit the usual symptoms. They could be so mild that they’re mistaken for something else.

A person could have the mutation and will develop the symptoms later on in life. Another reason is that an individual might only carry a pre-mutated gene, which means they’re not likely to actually get the disease, but there’s a good chance they will pass it on to their children.

Couples that may be planning on having children in the future may benefit from genetic testing because they’ll be able to determine ahead of time if they’re at risk of passing on the mutated gene. Parents who are at risk might decide they don’t want to have children because they don’t want to take the chance of their children having DM.

Discussing the options with a genetic counselor can help determine odds and risk factors involved and help couples make an informed decision.

Prenatal testing is when a fetus’s DNA is checked to see if they have the myotonic dystrophy mutation. This allows parents to know ahead of time if the baby will likely have the disease so they can best prepare.

Prenatal testing for DM is performed with a test called chorionic villus sampling, or CVS, or with another test called an amniocentesis.

Genetic counseling is a good option for many families that have children with myotonic dystrophy. This can be helpful is because it provides families with plenty of resources to help understand the disease better, such as how it’s inherited and what to expect in the future.

Understanding the Results

The results of genetic tests aren’t always simple to understand, especially for people who aren’t healthcare professionals. When the doctor goes over the results with you, it’s essential to ask any questions you have because they are something you’ll want to understand fully.

A genetic counselor can help you interpret the results and answer any questions you might have.

The results of genetic testing generally can confirm a person has myotonic dystrophy or determine if they’re at risk of developing it later in life. A negative test means the laboratory technician was not able to detect a change in the gene or chromosome that would indicate the presence of DM, meaning the patient is not currently at risk.

Sometimes the results of genetic tests aren’t entirely clear, which would mean the patient has to undergo further testing for a definitive answer. If this ends up being the case, the specialists and a team of health care professionals will be able to determine any other testing that needs to be performed.

DNA Tests Currently Available for Myotonic Dystrophy Include:

If you believe your child may have myotonic dystrophy or might develop it in the future, genetic testing is a good option so you can know for sure.

It can be performed by a number of professionals including your child’s primary care provider, a medical geneticist, specialist, or a nurse practitioner.

DNA tests usually require a blood sample, but some may ask for a swab of the inside of the cheek. Once the professional collects the DNA, the sample is then sent off to a laboratory.

Once it's examined by the technician, they send your healthcare provider a report with the results.

What Are the Chances That I Will Pass Myotonic Dystrophy on to My Child?

If one parent has myotonic dystrophy, there’s a 50 percent chance their child will also have the disease 3.

It does not make a difference if the parent is the mother or father; the chances are the same. If both parents do not have myotonic dystrophy, their offspring will also not have it.

Children that have congenital myotonic dystrophy, which is the most severe form of this disease, typically always inherit this condition from their mother.

Testing for Myotonic Dystrophy on a Pregnancy or Before a Pregnancy Is Achieved

During the 10-12th week of pregnancy, it’s possible to test the fetus for myotonic dystrophy with chorionic villus sampling, or CVS 4.

CVS can be performed two ways, transcervical and transabdominal. The transcervical method has a higher rate of miscarriage and it’s performed with plastic tubing inserted into the vagina through the cervix and into the placenta.

Transabdominal CVS is when a doctor inserts a needle into the abdomen and uterus, going into the placenta to collect a small tissue sample. It can take approximately two weeks to get the results of a CVS test.

Another way to test before a baby is born is with an amniocentesis, and this is performed during weeks 15 or 16. During this procedure, a needle is inserted into the abdomen to collect a sample of amniotic fluid for testing.

The fluid contains cells that have shed from the fetus, allowing doctors to determine if the baby has myotonic dystrophy or not.

These tests are both considered invasive testing and come with a small risk of miscarriage. It’s something that expecting parents must discuss in detail with their doctor to weigh the pros and the cons.

Who Does Myotonic Dystrophy Typically Affect?

Myotonic dystrophy is a disorder that affects men, women, children, and infants. Congenital DM1 is the most severe form and patients can show signs of this at birth.

Infants can experience severe lack of muscle tone, which is called hypotonia, and makes them appear “floppy.” Some infants with this condition are born with clubfoot and experience muscle weakness that affects both sides of their face.

Infants with congenital DM1 have problems with their vision and are often farsighted and have an abnormal curve of the eye lens, leading to blurry vision. Infants can have a hard time eating and experience failure to thrive. It is also common for infants to have breathing difficulties due to their muscle weakness.

Myotonic dystrophy type 2 is common in adults between the ages of 20 and 60 5. The most common symptoms associated with this type include muscle pain and weakness, cataracts, and myotonia.

Muscle weakness that affects the neck and fingers is usually the first sign of DM2, eventually developing into weakness in the hips. Heart abnormalities are less common amongst patients with DM2, but they can still happen.

Adult-onset DM1 is the most common form of this condition. The symptoms patients experience with this type vary greatly, some can have severe symptoms, while others have mild ones.

Sometimes DM1 can be associated with diabetes, cataracts, and myotonia. Men with this type typically end up going bald, which starts at the top center of their hairline. They can often become infertile as well.

Adults with DM1 may experience symptoms that have a very small impact on their quality of life, leaving them with a positive prognosis. DM1 symptoms usually start with weakness of the muscles that elevate the upper eyelids, muscles that help move the neck, muscles in the hands, lower leg muscles, and forearm muscles closest to the hands.

Some patients with DM1 may have muscles that take longer to relax after they have used them. DM1 patients can experience weakness in their facial muscles, leading to slurred speech, drooping eyelids, and a mask-like facial appearance.

DM1 can affect the heart, leading to defects that can impact the normal transfer of electrical impulses, leading to irregular heartbeat and an insufficient amount of carbon dioxide in the blood. Later in life, it’s possible for patients with DM1 to experience respiratory failure.

Myotonic Dystrophy Treatment Options

There is currently no cure for myotonic dystrophy. There are treatment options for managing the symptoms of this condition, but nothing that will make it disappear completely.

One of the most common treatment options for myotonic dystrophy is physical therapy.

Physical therapy is vital to strengthening the muscles and helping to better manage the pain in the musculoskeletal system. As muscles begin to weaken over time, patients may have to use walkers, scooters, canes, and/or braces so they can remain mobile.

Medications are available by prescription through the patient’s primary care physician to help manage pain. Skeletal muscle pain is most common in DM2 and can end up feeling worse in cold temperatures.

A doctor may suggest starting with over-the-counter pain medications first, as well as using heating pads and warm baths.

Breathing muscle weakness is common in DM1. A doctor may suggest using a breathing booster (small portable device) that helps pump air into the lungs at night with a face mask.

Some people with myotonic dystrophy are unable to cough due to muscle weakness. There are cough assist machines designed to clear out secretions, which can be especially helpful when they have a cold.

There can also be cognitive and behavioral abnormalities, which are more common in patients with DM1 that begins in childhood. People with these concerns generally have difficulties planning ahead, making decisions, and may end up developing an apathetic personality. Special education and an evaluation from a neuropsychologist can help.

Daytime sleepiness is something that DM1 and DM2 individuals can experience. Medication is used to help correct the body’s sleep and wake cycles, allowing them to sleep better at night.

Some of the most common medications used for this purpose are Ritalin, Provigil, and Nuvigil.

Before starting on medication, a doctor may suggest having the person go to sleep and wake up at the same time every day in an effort to get the body on a proper sleep schedule naturally.

The Prognosis for Myotonic Dystrophy

Myotonic dystrophy is a disease that affects individuals differently. It can vary quite a bit with DM1 and DM2 and it makes a difference in the prognosis if a patient started having symptoms as a child or an adult.

In many cases, DM2 is the least severe form and usually does not shorten an individual’s lifespan.

DM1 can be more serious and lead to life-threatening complications later in life, especially if an individual started experiencing symptoms when they were a child. The prognosis of patients with DM is typically hard to predict because of how differently it affects individuals.

Even two family members with the same type can experience completely different symptoms and health complications.

One of the best ways to make sure an individual has a good prognosis is to catch the disease as early as possible. There is no way to slow down or stop the disease from progressing, but symptom management at an early age can help individuals with this disease lead a normal life.

The life expectancy for patients with DM1 is a lot lower than DM2. This is because the most common causes of death are complications with cardiac and respiratory symptoms.

Does Myotonic Dystrophy Go Away?

It’s important for families to understand there’s currently no cure for myotonic dystrophy. There’s no form of treatment that can cure the disease and make it go away completely.

Catching the disease as early as possible with a physical examination or a genetic test is one of the best ways to start finding the best treatment options available to relieve your specific symptoms and to avoid complications that may develop.

People with myotonic dystrophy can experience very different symptoms, making a treatment plan something that differs between individuals. A professional healthcare team, especially someone who specializes in rare genetic diseases, can work closely with you to determine the best types of treatments available for the specific symptoms you experience.

Treatment is not a one size fits all type of thing. It can often take some trial and error for a doctor to find the best plan for disease management.

DM1 is often harder to predict than DM2 because the disease can progress and individuals can start having different symptoms, making treatment options difficult, but still possible.

Referenced Sources

  1. Myotonic Dystrophy.
    Genetics Home Reference. Reviewed: November 2010, Published: November 26, 2019.
  2. Myotonic Dystrophy (DM).
    Muscular Dystrophy Association. Retrieved online, 2019.
  3. How is Myotonic Dystrophy inherited?
    Myotonic Dystrophy Support Group. 2016.
  4. Genetic Testing for Myotonic Dystrophy. 03/18/2014.
  5. NM Update Course II: Inflammatory Myopathies/Myotonic Disorders.
    Richard J. Barohn, MD, Steven A. Greenberg, MD, Bassam A. Bassam, MD
    Bakri H. Elsheikh, MBBS, MRCP, Annabel K. Wang, MD, Gregory T. Carter, MD, MS, Andrew W. Tarulli, MD. September 2012.