Myotonic Dystrophy: Causes, Symptoms, Diagnosis and Treatment

It is muscular dystrophy, consisting of a group of more than 30 conditions that cause muscle weakness and degeneration.

As the condition progresses, it becomes more difficult to move.

Depending on the type and severity, the effects may be mild, progress slowly throughout everyday life, there may be a moderate disability, or it may be fatal.

Myotonic dystrophy (DM), also called myotonic dystrophy, atrophic myotonia, or Steinert’s disease, is a common form of muscular dystrophy.

Myotonic dystrophy is a hereditary disease. This form of muscular dystrophy causes myotonia, unable to relax the muscles after they contract.

Myotonia is exclusive to this type of muscular dystrophy.

It can affect the facial muscles, the central nervous system, the adrenal glands, the heart, the thyroid glands, the eyes, and the gastrointestinal tract.


Cause general weakness begins in the hands, feet, neck, or face muscles.

Little by little, it advances to involve other muscle groups, including the heart and a wide variety of other organ systems.

Four types of DM are determined by the time of onset of symptoms. These are:

  • Congenital: Severe symptoms are evident at birth.
  • Juvenile: Symptoms appear between birth and adolescence.
  • Adult: Symptoms appear in people 20 to 40 years old.
  • Late-onset: Mild symptoms appear after age 40.

Myotonic dystrophy is a rare disease that occurs in about one in 8,000 people.

The congenital form of DM is much rarer and occurs in only one in 100,000 births, and affects men and women equally.

Causes of myotonic dystrophy

The most common type of myotonic dystrophy is myotonic dystrophy type 1, which is caused by a mutation in a gene called myotonic protein kinase dystrophy (DMPK).

The DMPK gene is located on chromosome 19.

The specific mutation that causes myotonic dystrophy type 1 is repeated trinucleotide expansion. In people who have myotonic dystrophy type 1, a particular unit of the gene is repeated too many times, more than the normal range of five to 38 times, and therefore this section of the gene is too large and unstable.

The enlarged section of the gene is called trinucleotide repeat expansion.

People who have repeated numbers in the normal range will not develop type 1 myotonic dystrophy and can not pass it on to their children.

Having more than 50 repetitions causes myotonic dystrophy type 1.

People who have replays of 38-49 have a permutation.

They do not develop type 1 myotonic dystrophy, but they can pass type 1 myotonic dystrophy to their children.

Myotonic dystrophy has an effect called “anticipation.”

This means that when a person with repeated numbers in the premutation range has children, the expansion increases, and the child has a higher repetition number.

As a result, the disease symptoms tend to appear at an earlier age in the children concerning the time of the appearance in their affected parents.

Anticipation occurs more often when the inheritance comes from the mother’s genetic load. The more repetitions individuals have, the earlier the age of onset of symptoms is and the more severe they are.


The symptoms of DM vary in severity, and not all will have the onset of all the signs.

In general, myotonic dystrophy causes weakness and delays muscle relaxation called myotonia.

The disease somehow blocks the flow of electrical impulses through the muscle cell membrane.

Without an adequate flow of charged particles, the muscle can not return to its relaxed state once it has contracted.

The most severe form of DM is congenital myotonic dystrophy in newborns of mothers with type 1 myotonic dystrophy.

Congenital myotonic dystrophy is marked by severe weakness, poor suction and swallowing responses, respiratory distress, delayed motor development, and mental retardation.

Death in childhood is common in babies who have congenital myotonic dystrophy.

Symptoms of juvenile and adult-onset myotonic dystrophy include facial weakness and a loose jaw, drooping eyelids called ptosis, and muscle wasting of the forearms and calves.

A person with myotonic dystrophy has difficulty relaxing their grip, especially in the cold. Myotonic dystrophy affects the heart muscle and causes irregularities in the heartbeat.

It also affects the digestive system’s muscles, causing constipation and other digestive problems.

Myotonic dystrophy can cause cataracts in the eye, degeneration of the retina, low IQ, early frontal baldness, skin disorders, atrophy of the testicles, and diabetes.

It can also cause sleep apnea, a condition in which normal breathing is interrupted during sleep.

Myotonic dystrophy increases the need to sleep and decreases motivation.

Often, severe disabilities do not appear until approximately 20 years after symptoms begin.

Although these diseases affect the ability to walk, most people who have myotonic dystrophy can walk for much longer in their lives.

Some people who have a repeat expansion of trinucleotides in their DMPK gene do not have DM symptoms or have very mild symptoms and manage to go unnoticed.

It is not unusual for a woman to be diagnosed with DM after having a baby with congenital myotonic dystrophy.

While your symptoms may affect your quality of life, most signs are not life-threatening. People with myotonic dystrophy often live a long life.


The diagnosis of myotonic dystrophy may be masked because the symptoms may begin at any age, may be mild or severe, and may occur with a wide variety of associated conditions.

The diagnosis of myotonic dystrophy begins with a careful medical history and a thorough physical examination to determine the distribution of symptoms and rule out other causes.

A family history of myotonic dystrophy helps establish the diagnosis.

The genetic tests, usually using a blood sample, establish a definitive diagnosis of myotonic dystrophy.

The DNA in the blood cells is examined, and the number of repetitions in the affected gene is determined.

Other tests may help establish the diagnosis, but only rarely will other tests be needed.

An electromyogram (EMG) examines how muscles respond to stimulation.

The characteristic changes revealed by this test and observed in myotonic dystrophy help distinguish it from other muscular diseases.

Removing a small piece of muscle tissue for microscopic examination is called a muscle biopsy.

Myotonic dystrophy is marked by characteristic changes in the structure of muscle cells that can be seen in a muscle biopsy.

An electrocardiogram could be performed to detect anomalies in the heart rhythm associated with myotonic dystrophy.

These symptoms often appear later in the course of the disease.

If genetic tests in a family have identified a DMPK mutation, it is possible to examine a fetus during pregnancy.

Tests can be performed at 10-12 weeks of gestation using a procedure called chorionic villus sampling (CVS), which involves removing a small portion of the placenta and analyzing the DNA of your cells.

It can also be performed by amniocentesis after 14 weeks of gestation by sampling a small amount of the amniotic fluid surrounding the fetus and subsequently analyzing the cells in the liquid.

Each of these procedures carries a small risk of miscarriage.


Myotonic dystrophy can not be cured, and no treatment can delay its progression.

However, many of its symptoms can be treated.

Physical therapy can help preserve or increase the strength and flexibility of the muscles.

The ankle and wrist devices can support weakened limbs.

Physical therapy consists of:

1.- General exercises

A range of movements and stretching exercises can help combat the inevitable inward movement of the limbs as the muscles and tendons shorten.

Members tend to stay fixed on their position, and these types of activities can help keep them mobile for longer.

Standard low-impact aerobic exercises such as walking and swimming can also help.

2.- Respiratory assistance

As the muscles used to breathe become weaker, it may be necessary to use devices to help improve the oxygen supply at night.

In the most severe cases, the patient may need a respirator constantly.

Assistance for mobility: Canes, wheelchairs, and walkers can help the person keep moving.

3.- Frenillos

They keep muscles and tendons stretched and help reduce their shortening.

They also give additional support to the user when they move.

Irregularities in the heartbeat can be treated with medications or a pacemaker.

In general, an annual electrocardiogram is recommended.

The two most commonly prescribed medications for muscular dystrophy are Corticosteroids. This medication can help increase muscle strength, but long-term use can weaken bones and increase weight gain and heart medications.

Beta-blockers and angiotensin-converting enzyme (ACE) inhibitors may help if the condition affects the heart.

Diabetes mellitus in myotonic dystrophy is treated the same way as in the general population.

A diet high in fiber can help prevent constipation. Lens replacement surgery is available when cataracts develop.

Occupational therapy is used to develop tools and techniques to help the patient become more independent, improve skills, and compensate for the loss of strength and agility.

A language therapist can provide training for weakness in the muscles that control speech and swallowing.