Congenital Myopathy

What is congenital myopathy?

Congenital myopathy is a rare genetic condition that causes muscle weakness. Congenital means “present at birth” and myopathy means “disease of muscle.” Babies with congenital myopathies lack muscle tone at birth. Other signs of the condition include skeletal problems (like weak or improperly aligned bones), difficulty breathing and feeding issues. Symptoms can appear at birth, during infancy or throughout childhood.

What are the different types of congenital myopathy?

There are six main types of congenital myopathy, but other rare types have also been identified. The different types vary in symptoms, severity, treatment options and outlook.

The six main types of congenital myopathy are:

Central core disease

Central core disease is a type of core myopathy. Core myopathies are the most common type of congenital myopathy. Typically, floppiness (hypotonia) is seen in infants. Children have delayed milestones and moderate arm and leg weakness. However, weakness doesn’t seem to worsen over time. A change (mutation) in the RYR1 gene causes central core disease.

Minicore (multicore) disease

Minicore (multicore) disease is another type of core myopathy. It has many subtypes. Most subtypes include severe weakness in the arms and legs. Scoliosis (spine curve) is also frequently seen. Breathing difficulties are common, and weakened eye movements can occur. A mutation in the RYR1 gene or another gene causes multicore disease.

Nemaline myopathy

Nemaline myopathy is another common congenital myopathy. Babies with nemaline myopathy typically have breathing problems and feeding issues. They also frequently have weakness in their face, neck, arms and legs. In addition, skeletal complications such as scoliosis can occur. A mutation in one of several genes, including NEM2, ACTA1 andTPM2, causes nemaline myopathy.

Centronuclear myopathy

Centronuclear myopathy is a very rare congenital myopathy. Symptoms include weakness in your baby’s arms, legs and face, droopy eyelids and problems with eye movement. Weakness tends to worsen over time. A mutation in the DNM2, BIN1 or RYR1 gene causes centronuclear myopathy.

Myotubular myopathy

Myotubular myopathy is a rare kind of congenital myopathy that usually only affects male babies. Floppiness and weakness are very severe. Breathing and swallowing difficulties are common. A condition called osteopenia (weak bones) is common as well. Many children don’t survive their first year of life. A mutation in the MTM1 gene causes myotubular myopathy.

Congenital fiber-type disproportion myopathy

Congenital fiber-type disproportion myopathy is a rare condition that starts with floppiness. Symptoms include face, arm and leg weakness along with breathing difficulties. Most infants are severely affected, but their respiratory function can improve with age. Mutations in the TPM3 gene, ACTA1 gene, TPM2 gene, MYH7 gene and RYR1 gene have been found in children with congenital fiber-type disproportion myopathy.

What are the symptoms of congenital myopathy?

Symptoms of congenital myopathy can vary depending on the type. They can be present at birth or develop throughout infancy and childhood. The most common symptoms of congenital myopathy include:

• Floppiness (hypotonia): Loss of your child’s muscle tone that may progress over time.
• Muscle weakness: Muscles in your child’s neck, shoulders and pelvis (proximal muscles) are most commonly affected.
• Difficulty breathing: Feeling short of breath or like you can’t fill your lungs with air because of the weakness of breathing muscles.
• Developmental delays: Milestones such as sitting up or turning over aren’t met as expected.
• Feeding issues: Sucking from breast or bottle, eating from a spoon, chewing and drinking can all be abnormal and difficult.
• Falling/stumbling: Toddlers may fall or stumble due to muscle weakness.

What causes congenital myopathy?

Changes (mutations) in specific genes cause most congenital myopathies. The changes in these genes cause problems in your child’s muscles, the nerves that stimulate your child’s muscles and your child’s brain.

How is congenital myopathy diagnosed?

Your child’s healthcare provider at birth, generally a neonatologist or pediatrician, will perform a physical exam to diagnose congenital myopathy. They may request several tests to confirm the diagnosis and will refer you to a neurologist and perhaps a geneticist. These tests include:

• Blood test: A blood test can check for increased levels of a muscle enzyme called creatine kinase.
• Electromyogram (EMG): An EMG can measure the electrical activity of your child’s muscles.
• Muscle biopsy: A muscle biopsy can look at cell changes in your child’s muscles.
• Genetic testing: Genetic testing can look for changes in the genes that cause myopathy.

How is congenital myopathy treated?

Treatment for central core disease and multicore disease may involve the use of a drug called albuterol. Albuterol is considered experimental but has been shown to help lessen the amount of weakness your child experiences. However, it’s not a cure for the disorder.

Treatment for all types of congenital myopathy involves managing your child’s symptoms. These treatments should include:

• Orthopedic treatment, if needed.
• Physical therapy.
• Occupational therapy.
• Speech therapy.

Further experimental treatments like gene therapies are still being developed.

How can I reduce my risk of having a child with congenital myopathy?

Because congenital myopathy is the result of a genetic change (mutation), the disorder can’t be prevented. If you’re concerned about having a baby with a genetic condition, you should talk with your healthcare provider about genetic counseling and possible genetic testing.

What can I expect if my child has congenital myopathy?

The prognosis for congenital myopathy varies greatly depending on the type and severity of your child’s condition. Congenital myopathy can lead to long-term skeletal problems such as:

• Reduced joint mobility.
• Hip issues.

Life expectancy varies as well. If your baby has severe breathing trouble, they may experience respiratory failure or complications such as pneumonia. However, if your child has a mild condition, they may grow up to live a full life. Talk to your child’s healthcare provider about your child’s specific condition.

What’s the difference between congenital myopathy and muscular dystrophy?

Muscular dystrophy is also a genetic condition that causes muscle weakness. However, there are several differences. With congenital myopathy, symptoms are present at birth or develop during infancy or childhood. With muscular dystrophy, some people have symptoms at birth, but others develop symptoms throughout childhood or adulthood.

With muscular dystrophy, the muscles tend to degenerate and regenerate. Muscular dystrophy is a progressive disease, which means symptoms may get worse over time. In addition, the heart and lungs are often affected over time. Lab tests can help distinguish the two diseases.

A note from Cleveland Clinic

Receiving the news that your baby has a rare inherited condition can be difficult and overwhelming. However, a team of specialists will work with you to prolong the life of your child and make them as comfortable and functional as possible. Support is available to help you and your family navigate your child’s diagnosis or to help you cope with an unexpected loss. If you have a family history of myopathy and plan on becoming pregnant, discuss genetic testing with your healthcare provider. They may be able to help you identify your risk of having a child with a genetic condition.