Muscular dystrophy

A diagnosis of muscular dystrophy comes with a lot of questions and uncertainty about your child’s health, like:

• What is it?
• What causes it?
• What should I do when my child is diagnosed?
• What are the treatments?
• What’s the long-term outlook for my child?

At Children’s Hospital Boston, we know how important it is for you to fully understand your child’s condition and prognosis. We’ve provided key information about MD here, and when you meet with our team of doctors, they’ll be able to explain your child’s individual circumstances and treatment options.

What is muscular dystrophy?

• MD is a group of diseases in which a genetic mutation causes muscle tissue and fiber to be more susceptible to damage.

• DMD and BMD are caused by a defect in the gene that makes dystrophin, an important muscle protein. Without enough dystrophin, muscle tissues break down and weaken.

• Children with MD gradually experience greater difficulty in moving their arms and legs.  Motor tasks in general may become more difficult.  Difficulty breathing may occur.

• MD is genetic, which means that children are born with the mutation that causes the disease.

• In some cases, children with MD may experience problems with learning and behavior. This is most extensively documented in DMD and BMD.

What are the different types of MD?

The two most common types of MD in children are:

Duchenne muscular dystrophy (DMD)

• DMD is the most common form of MD, affecting about oneout of every 3,500  - 4,500 males

• It’s caused by a defect in the gene that makes the protein dystrophin.

• DMD causes progressive weakening of muscles.

• Symptoms usually appear when a child is between ages of 3 and 5.

Becker muscular dystrophy (BMD)

• BMD is another common form of MD, affecting about one in every 30,000 – 40,000 males.

• This form is similar to DMD, but it’s caused by a milder mutation on the dystrophin gene.

• BMD symptoms are less severe and progress more slowly than symptoms of DMD.

• BMD is usually , but not always, diagnosed later than DMD.

Other relatively common forms of MD include:

Myotonic muscular dystrophy (MMD)

• MMD affects about one in 8,000 people. Symptoms often begin in childhood.

• MMD is autosomal dominant, which means that if one parent has the disease, there is a 50 percent chance that they will pass MMD to the child, and that both girls and boys are equally affected.

There are two major types of MMD: Type 1 and Type 2:

• Type 1 MMD (DM1) is the most common. It occurs when a portion of the DMPK gene on chromosome 19 is too large.

• Congenital myotonic dystrophy is a variant of type 1 MMD that begins in infancy. Babies born with congenital MD have severe weakness in their skeletal muscles, often including  the ones that control breathing and swallowing, which can lead to serious respiratory problems early in life.  However, these infants often improve if properly supported.

• Type 2 MMD (DM2) is less common than DM1 and tends to be milder. It’s caused by a defect in the ZNF9 gene on chromosome 3.  DM2 has not been reported in children to date.

• Symptoms of DM1 can appear at any time from early childhood to adulthood.

Facioscapulohumeral muscular dystrophy (FSHD)

• FSHD affects about five in 100,00 people. This form of MD is autosomal dominant, which means that it occurs equally in males and females.

• This type of MD progresses slowly and is generally mild, so it’s usually not diagnosed until the late teens or in early adulthood.

• FSHD is one of the few forms of MD that causes asymmetric weakness (for example, weakness in the left arm but not the right).

Causes

What causes muscular dystrophy?

Muscular dystrophy is caused by a problem in the genes. Genes determine all of our traits, such as eye color and blood type. They are contained in the cells of our bodies on stick-like structures called chromosomes.

Normally, there are 46 chromosomes in each cell of our body, or 23 pairs. One of these pairs, called the “sex chromosome pair,” determines gender. Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY).

About genes and MD:

• DMD and BMD are caused by a mutation on an X-linked recessive gene called dystrophin. X-linked means that the gene that causes the trait or disorder is found on the X-chromosome.

• In order for a female to have DMD or BMD, she has to have dystrophin mutations on both of her X-chromosomes, which is extremely rare.

• Since a male only has one X-chromosome, he only needs to have the gene on that single X chromosome to have the disorder.  Almost all patients with DMD and BMD are male.

• A woman might be a carrier and unknowingly have the gene on only one of her X chromosomes (so she will not have MD), and pass it on to her son, who will have the disorder if that is the X chromosome he gets from her.  A female carrier is at risk for cardiac complications and thus should have periodic cardiac screening.

Signs and symptoms

What are the symptoms of MD?

Muscular dystrophy can affect your child physically, cognitively and behaviorally. The physical symptoms of MD depend on what form of the disease your child has. Even then, the severity of symptoms can vary widely from child to child.

Symptoms of Duchenne muscular dystrophy (DMD)

Symptoms of DMD usually appear between the ages of 3 and 5. They can include:

• difficulty walking
• tripping or falling
• trouble with climbing or descending stairs
• walking on the toes
• inability to run as fast as other boys his age
• calf pseudohypertrophy (large calf muscles)
• learning disabilities
• cardiac complications (usually occur later in the course)

Symptoms of Becker muscular dystrophy (BMD)

Since BMD symptoms are milder and progress more slowly than those associated with DMD, this form of MD is usually diagnosed later than DMD. In some cases, a child may not show any symptoms at all, and is only diagnosed after specific blood tests come back with abnormal results.

Symptoms of BMD include:

• difficulty walking

• weakness in pelvic, shoulder and back muscles

• cardiac complications

Symptoms of Myotonic muscular dystrophy (MMD)

Symptoms of MMD can appear anytime from early childhood to adulthood. They include:

• “distal weakness” (weakness in the hands and feet), a characteristic pattern in DM1 especially

• myotonia (difficulty relaxing muscles once they contract)

• cardiac complications

• eye problems

• diabetes

• daytime sleepiness

Symptoms of Facioscapulohumeral Muscular Dystrophy (FSHD)

Symptoms of FSHD can start at any time, but since they tend to be very mild, a lot of people are not diagnosed until their teenage years. These symptoms can include:

• typically, a child first experiences weakness in the facial muscles (facio) shoulder girdle (scapulo) and upper arms (humeral). 

• weak shoulder blade muscles, leading to shoulder blades that may protrude

• weak upper arm muscles (other muscles may also be weak)

• asymmetric weakness (for example, when the left thigh muscle is weak and the right is normal)

How does MD affect a child behaviorally and cognitively?

Many children with MD have normal intelligence and normal behavior. However, the incidence of behavioral and cognitive issues is higher in children with DMD and BMD than in the general population.

Behavioral effects:

All children (and especially adolescents and teens) experience emotional ups and downs—and not every child with a chronic illness requires mental health support. 

You should watch carefully for the following signs that your child’s behavior may require professional evaluation:

• reports of behavioral problems in school and problems with attention span (such as ADHD)

• his behavior regresses (he becomes overly dependent on parents or medical caregivers)

• he expresses acute frustration at not being able to walk, including throwing tantrums

• he seems overwhelmed or consumed by the emotional toll of his illness

• he exhibits frequent bouts of irritability and anger

• he resists or avoids following his treatment plan (including skipping medication or missing medical appointments)

• he withdraws from peers or gives up on taking part in age-appropriate activities and gatherings

You should be an active and informed participant in your child’s physical and mental health care, and keep lines of communication open and honest.

Cognitive effects

Some children with MD also experience cognitive symptoms that areunrelated to behavior.

The degree of cognitive and intellectual disability that a child with MD will experience can vary widely, ranging from none to mild to moderate to severe. For example, learning disabilities can range from ADHD to autism.

What does “mild to moderate intellectual disability” mean?

Children with mild intellectual disability are usually able to do everyday things like read, hold a job and take public transportation independently. Children with moderate intellectual disability need more support. 

Questions to ask your doctor

You probably have a lot of questions on your mind before meeting with your child’s doctor for the first time. At the appointment, it can be easy to be overwhelmed with information and forget the questions you wanted to ask.

A lot of parents find it helpful to jot down questions beforehand. That way, when you talk to your child’s clinician, you can be sure that all your concerns are addressed. Remember that physicians are open to learning from families too. Attend conferences, read up on updated materials and don’t be afraid to share what you have learned.

Some questions you might ask include:

• How should I talk to my child about her condition and the long-term outlook?
• How should I explain my child’s condition to others?
• Which medication might my child need to take and what are the possible side effects?
• How should I monitor and support my child’s mental and emotional health?
• Do I need to make any other changes to my child’s home and school routines?
• What other resources can you point me to for more information?