Myotonic dystrophy, also known as Steinert disease, is a genetic disorder marked by difficulty relaxing muscles after they contract. People with this condition may have trouble releasing a doorknob or letting go after a handshake.
This type of muscular dystrophy affects both men and women and is most common in young adults. It mainly involves the muscles of the face, neck, hands, feet, and forearms.
In some cases, myotonic dystrophy can be severe, causing major muscle impairment and leading to a life expectancy of around 50 years. In others, symptoms may be much milder and limited mostly to muscle weakness.
Common symptoms
The main symptoms of myotonic dystrophy include:
-
Muscle atrophy;
-
Frontal baldness;
-
Intellectual disability;
-
Difficulty feeding;
-
Breathing difficulties;
-
Cataracts;
-
Difficulty relaxing a muscle after contraction;
-
Speech difficulties;
-
Excessive sleepiness;
-
Diabetes;
-
Infertility;
-
Menstrual irregularities.
Depending on the severity of the condition, stiffness caused by genetic changes can affect multiple muscle groups, which may lead to death before age 50. People with the mildest form usually experience only muscle weakness.
Diagnosis is made based on an evaluation of symptoms and genetic testing, which can identify chromosomal changes.
Different types
Myotonic dystrophy is classified into 4 types:
-
Congenital: Symptoms appear during gestation (in utero), when the baby shows reduced fetal movement. Soon after birth, the newborn may have difficulty breathing and noticeable muscle weakness;
-
Childhood-onset: In this type, the child develops normally during the first years of life, with symptoms appearing between ages 5 and 10;
-
Classic: Classic myotonic dystrophy appears only in adulthood;
-
Mild: People with the mild form of myotonic dystrophy do not have significant muscle impairment, only mild weakness that can be managed.
The condition is caused by genetic alterations on chromosome 19. These changes can become more pronounced from one generation to the next, resulting in more severe symptoms.
Treatment options
Treatment for myotonic dystrophy focuses on relieving symptoms, supporting muscle function, and managing the multisystem complications associated with the condition.
Medications commonly used to reduce muscle stiffness and improve myotonia include mexiletine, which is considered the first-line option for myotonia when cardiac evaluation shows it is safe to use. Lamotrigine may be used when mexiletine is not tolerated or is contraindicated.
Physical therapy is essential to improving quality of life. It can help increase range of motion, muscle strength, and coordination, supporting better function in daily activities.
Treatment may also involve cardiac monitoring, respiratory evaluation and support, ophthalmologic care, endocrine management, speech and swallowing therapy, and genetic counseling. This coordinated approach helps reduce symptoms, prevent complications, and improve long-term outcomes.