Congenital myopathies

Overview

Congenital myopathies are rare muscle diseases mostly present at birth (congenital) that result from genetic defects. There are many different types of congenital myopathies, but most share common features, including lack of muscle tone and weakness.

Other signs and symptoms of some congenital myopathies include feeding and breathing difficulties, as well as skeletal conditions, such as curvature of the spine (scoliosis), weak bones (osteopenia) or hip problems. Signs and symptoms of congenital myopathies may not be apparent until later in infancy or childhood.

There are no known cures for congenital myopathies. However, the recent advances in gene therapy can provide treatment for congenital myopathies. The supportive treatments, including physical, occupational and speech therapies, nutritional support, and assisted breathing, may be helpful. Genetic counseling may help assess the risk of congenital myopathies in future pregnancies.

Symptoms

Signs and symptoms vary depending on the type of congenital myopathy. The severity of signs and symptoms also varies, though the conditions are often stable or slowly progressing.

Common signs and symptoms include:

Lack of muscle tone
Muscle weakness
Delayed motor skills
Noticeable facial weakness
Drooping eyelids
Muscle cramps or contractions

There are different types of congenital myopathies, some of which include:

Central core disease. This condition causes muscle weakness and developmental problems. Some people may develop a significant reaction to general anesthesia (malignant hyperthermia).
Centronuclear myopathies. These rare conditions cause muscle weakness in the face, arms, legs and eye muscles, and breathing problems.
Congenital fiber type disproportion myopathy. Small fibers are found on muscle tissue during a biopsy. This condition causes muscle weakness in the face, neck, arms, legs and trunk.
Nemaline myopathy. Nemaline myopathy is one of the more common congenital myopathies and causes muscle weakness in the face, neck, arms and legs, and sometimes scoliosis. It may also cause breathing and feeding problems.
Multiminicore disease. This condition has several subtypes and often causes severe muscle weakness in the arms and legs, and scoliosis.
Myotubular myopathy. This rare condition, which occurs only in males, causes muscle weakness, floppiness and breathing problems.
Other myopathies. Other rare myopathies include autophagic vacuolar myopathy, cap disease, congenital myopathy with arrest of myogenesis, myosin storage (hyaline body) myopathy and zebra body myopathy.

When to see a doctor

Congenital myopathies are usually noticed at birth. But if you notice a lack of muscle tone or delayed motor skills as your baby grows, let your child's doctor know about your concerns.

Causes

Congenital myopathies are caused by one or more genetic abnormalities in genes that control muscle development.

Risk factors

The only known risk factor for congenital myopathies is having a blood relative with one of these conditions, or one or both parents who carry a mutated gene that causes them.

Complications

Congenital myopathies are associated with a number of complications, such as:

Delays in motor skills
Scoliosis
Pneumonia
Respiratory failure
Feeding problems

Prevention

There's no way to prevent congenital myopathies. If you're at high risk of having a child with a congenital myopathy, you may want to consult a genetic counselor before becoming pregnant.

A genetic counselor can help you understand your chances of having a child with a congenital myopathy. He or she can also explain the prenatal tests that are available and help explain the pros and cons of testing.

Diagnosis

To diagnose the condition, your doctor will review your medical and family history. He or she will conduct a physical and a neurological examination to find the cause of the muscle weakness and rule out other conditions. Your doctor may conduct several tests to diagnose congenital myopathy.

Blood tests. These may be ordered to detect an enzyme called creatine kinase.
Electromyography (EMG). Electromyography measures electrical activity within muscles.
Genetic testing. This may be recommended to verify a particular mutation in a given gene.
Muscle biopsy. A specialist may remove and examine a small sample of tissue (biopsy) from your muscle.

Prenatal diagnosis

If you have a known family history of congenital myopathies, you can opt for minimally invasive prenatal testing. Chorionic villus sampling can be done after 11 weeks of pregnancy. Amniocentesis can be done after 15 weeks, and cordocentesis can be done shortly after that.

The risk of pregnancy loss associated with these tests is less than 1%.

Treatment

Congenital myopathies can't be cured, but doctors can help you manage the condition and symptoms. Treatment may include several options.

Genetic counseling. Genetic counselors may help you understand the genetics of the condition.
Medications. Medications may help treat symptoms of some myopathies. For example, the drug albuterol (Proair HFA, Ventolin HFA, others) may be helpful in some congenital myopathies.
Nutritional and respiratory support. Nutritional or respiratory support may be needed as the condition progresses.
Orthopedic treatments. Orthopedic support devices or other treatments, such as surgery to correct or improve scoliosis or contractures, may be helpful.
Physical, occupational or speech therapy. Physical, occupational or speech therapy may help manage symptoms. Low-impact aerobic exercise, such as walking and swimming, can help maintain strength, mobility and general health. Some types of strengthening exercises also might be helpful.
Respiratory therapy. Some patients need respiratory support or respiratory treatments.

In addition to these treatments, some people with congenital myopathies may benefit from an evaluation from an endocrinologist. An endocrinologist can monitor bone health, as bone diseases such as osteopenia and osteoporosis may develop in some people with congenital myopathies.

It's also important to take precautions to prevent respiratory infections. Annual influenza vaccinations and regular pneumonia vaccinations are recommended. Try to avoid contact with anyone who has an obvious respiratory infection.

Coping and support

When you learn your child has a congenital myopathy, you may experience a range of emotions, including anger, fear, worry, sorrow and guilt. You may not know what to expect, and you may worry about your ability to care for your child. The best antidote for fear and worry is information and support.

Consider these steps to prepare yourself and to care for your child:

Find a team of trusted professionals. You'll need to make important decisions about your child's education and treatment. Build a team of health care providers, teachers and therapists you trust. These professionals can help evaluate the resources in your area and explain state and federal programs for children with disabilities.
Seek out other families who are dealing with the same issues. Ask your doctor if your community has a support group for parents of children with congenital myopathies. You can also find internet support groups. Family and friends also can be a source of understanding and support.

Preparing for an appointment

Congenital myopathies are often evident at birth. But, the effects of some congenital myopathies may not appear until childhood or later. If this is the case, you'll likely start by seeing your child's pediatrician or a primary care doctor.

What you can do

Write down any signs and symptoms your child is experiencing. Write down when each symptom began.
Write down your child's family history, including details from both the maternal and paternal sides of the family.
Ask a family member or friend to come with you, if possible. Sometimes it can be difficult to remember all of the information provided to you during an appointment. Someone who accompanies you might help you remember the doctor's recommendations.
Write down questions to ask your doctor.

Your time with your doctor may be limited, so preparing a list of questions may help you make the most of your time together. You might want to ask the following questions:

What's the most likely cause of these symptoms?
What kinds of tests does my child need? Do these tests require any special preparation?
Does my child need treatment? If so, when?
What treatments are available, and which do you recommend?
What is the prognosis?
If I have more children, what are the odds of this condition occurring in them?
Are there any brochures or other printed material that I can take home with me? What websites do you recommend visiting?

What to expect from your doctor

Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over any points you want to spend more time on. Your doctor may ask: