Nemaline Myopathy

What is nemaline myopathy?

Nemaline myopathy (NM) is a condition that affects the muscles your body uses to move (skeletal muscles). Nemaline myopathy causes muscle weakness (myopathy) in many places in your body. Symptoms can occur at birth, during childhood or, rarely, in adulthood. Muscle weakness tends to be worse in your:

• Face.
• Neck.
• Pelvis.
• Shoulders.
• Upper arms and legs.

Nemaline myopathy also leads to rod- or thread-like materials (nemaline bodies) in your muscles. Your provider sees the nemaline bodies when they biopsy your muscles. “Nema” means thread-like in Greek.

Other names for nemaline myopathy include:

• Congenital rod disease.
• Nemaline body disease, nemaline rod disease or nemaline rod myopathy.
• Rod body disease, rod-body myopathy or rod myopathy.

Most people inherit nemaline myopathy from one or more gene changes (mutations) passed down from their parents. Some people with nemaline myopathy have a spontaneous gene mutation.

There is no cure for nemaline myopathy. Treatment focuses on relieving your specific symptoms. Most people with the most common form of NM can lead full, active lives.

Are there different types of nemaline myopathy?

The six main types of nemaline myopathy are:

• Typical congenital nemaline myopathy: This is the most common type of nemaline myopathy. It accounts for about half of all cases of NM.
• Intermediate congenital nemaline myopathy: This type causes fewer symptoms than the severe congenital type and more symptoms than the typical congenital type. It accounts for roughly 20% of cases.
• Severe congenital (neonatal) nemaline myopathy: This condition shows up at birth. It accounts for about 16% of cases.
• Childhood-onset nemaline myopathy: This type occurs between ages 10 and 20. It accounts for just over 10% of cases.
• Adult-onset nemaline myopathy: This condition occurs between ages 20 and 50. It accounts for about 4% of cases.
• Amish nemaline myopathy: This type affects the Amish community. It accounts for just a few cases. It often leads to death in early childhood.

Who might get nemaline myopathy?

Nemaline myopathy can affect anyone no matter their gender, ethnicity or race. But you’re at greatest risk of this condition if one or both of your parents carry the gene mutation for NM. Members of the Amish community are also at higher risk.

How common is nemaline myopathy?

Nemaline myopathy is a rare condition. Researchers estimate that NM occurs in 1 out of 50,000 live births. However, 1 out of 500 people in the Amish community may have NM.

What causes nemaline myopathy?

Nemaline myopathy is a disease of the musculoskeletal system. Genetic changes (mutations) usually cause NM. Either one or both of your parents may carry this gene mutation. Nemaline myopathy can occur when you inherit one abnormal gene from each parent (autosomal recessive genetic condition). Less commonly, it can occur when one parent passes down an abnormal gene (autosomal dominant genetic condition). A new gene change that spontaneously occurs in an egg or sperm cell can also cause NM.

Most commonly, mutations of the nebulin (NEB) or actin alpha-1 (ACTA1) genes cause nemaline myopathy. Nebulin and actin are proteins that are part of the sliding molecular machinery that shortens muscles.

What are the symptoms of nemaline myopathy?

The main symptoms of nemaline myopathy include:

• Diminished muscle tone (hypotonia).
• Lessened or no reflexes.
• Muscle weakness.

NM symptoms in infants may also include:

• Abnormal waddling walk (gait disorder).
• Delayed motor skills, such as sitting up, standing and controlling your head.
• Difficulty speaking (dysarthria) and swallowing (dysphagia).
• Displaced jaw, farther back than normal (retrognathia).
• Elongated face.
• Extremely arched roof of the mouth.
• Nasally speech (velopharyngeal dysfunction).
• Poor breathing during sleep (nocturnal hypoventilation), leading to increased carbon dioxide in your blood (hypercarbia).
• Shortness of breath (dyspnea).

As people with NM get older, symptoms may include:

• Abnormal spine rigidity.
• Scoliosis.
• Shortening or tightening of your joints (joint contractures).
• Sunken chest (pectus excavatum).

How is nemaline myopathy diagnosed?

A healthcare provider will first ask about your symptoms — or your child’s symptoms — and your family history. They will also do a physical exam.

If your provider suspects nemaline myopathy, they will do a biopsy. This means your provider surgically removes and tests muscle tissue. If you have (or your child has) NM, a biopsy will show thread- or rod-like shapes (nemaline bodies) in the muscle tissue.

Your provider may recommend genetic testing. This can confirm a nemaline myopathy diagnosis.

How is nemaline myopathy treated?

Nemaline myopathy treatment focuses on reducing your symptoms. Treatments may include:

• Breathing support with a tracheostomy, mechanical ventilation or a bilevel positive airway pressure (BiPAP) machine.
• Low-impact exercise, to help with muscle strength.
• Massage therapy and physical therapy, to maintain muscle function.
• Speech therapy, to improve speech problems or nasally speech.
• Stretching techniques, to increase muscle movement.
• Walking devices, such as a cane, crutches, knee braces, splints or a wheelchair.

People with serious symptoms or other health complications may need hospitalization. Treatments in the hospital may include:

• Respiratory support, such as mechanical ventilation to help with breathing while sleeping.
• Surgery, to help treat joint contractures or scoliosis.
• Tube feeding (enteral nutrition), to help with feeding problems.

How can I reduce my risk or my child’s risk of nemaline myopathy?

You can’t reduce your risk of NM or your child’s. But you can look for the signs so your child can get prompt monitoring and treatment if needed.

What can I expect if I have (or my child has) nemaline myopathy?

What you can expect varies depending on the type of NM:

Typical congenital nemaline myopathy

Muscle weakness generally stays the same over time, though weakness may increase during puberty growth spurts.

Severe congenital (neonatal) nemaline myopathy

Complications may include:

• Arthrogryposis multiplex congenita (when many joints become fixed in either bent or straightened positions).
• Aspiration pneumonia.
• Bone fractures.
• Cardiomyopathy.
• Respiratory failure.

Intermediate congenital nemaline myopathy

Many people need breathing support and a wheelchair.

Childhood-onset nemaline myopathy

This condition may lead to inability to bend your foot up toward your leg (foot drop). It can progress to inability to move your ankles and lower leg muscles.

Adult-onset nemaline myopathy

Complications may include:

• Breathing complications.
• Difficulty holding up your head due to weak neck muscles.
• Heart complications.
• Increasing muscle weakness.

Amish nemaline myopathy

Complications may include:

• Increasing muscle weakness.
• Insufficient respiratory function.
• Muscle atrophy.

What is the outlook if I have (or my child has) nemaline myopathy?

The outlook varies depending on the type of NM and the severity of your symptoms. If you have the most mild type of NM (typical congenital nemaline myopathy), you may be able to walk unassisted. People with the most serious type of NM (Amish nemaline myopathy) often only live until age two.

There is no cure for nemaline myopathy. But many people with NM can lead long lives with proper treatment. Depending on the type of NM, life expectancy ranges from a few months to a full lifetime.

How do I take care of myself or my child with nemaline myopathy?

You can help to reduce complications if you:

• Have your heart function regularly monitored.
• See your provider immediately for treatment of any lower respiratory infections, such as bronchitis, chest infection or pneumonia.

If you carry the gene for NM and you’re considering becoming pregnant, you may want to consult a genetic counselor.

A note from Cleveland Clinic

Nemaline myopathy (NM) is a rare condition that affects your skeletal muscles. The main symptoms include decreased muscle tone and muscle weakness. The six types of nemaline myopathy differ by timing and severity of symptoms. There is no cure for NM, but healthcare providers focus on reducing symptoms. With proper treatment, many people with the most common form of NM (typical congenital nemaline myopathy) can lead independent lives. The outlook for other types of NM varies based on severity of symptoms.