A rare muscular disorder that causes muscle weakness, reduced muscle tone, and poor reflexes is called nemaline myopathy (NM). Usually, doctors diagnose this condition by performing a biopsy. To treat this condition, doctors usually focus on managing the symptoms, exercise, therapy, and respiratory support.
In other words, nemaline myopathy is a muscle disorder that negatively affects the muscles the body uses to move (also known as skeletal muscles). While muscle weakness may occur anywhere in the body, this condition mostly affects the muscles in the following parts of the body. For example, the face, neck, pelvic area, shoulders, upper arms, and legs.
Moreover, this condition may also lead to rod- or thread-like material (also called nemaline bodies) in the muscles. These bodies can be seen during a biopsy. In some cases, this condition is called congenital (present at birth) rod disease, nemaline body disease, nemaline rod disease, nemaline rod myopathy, rod body disease, rod-body myopathy, or rod myopathy.
While most people inherit this condition by receiving either one or two copies of the abnormal gene from their biological parents, sometimes it occurs due to a new gene mutation. Unfortunately, there is no way to cure this disorder. That’s why the treatment goal is to relieve the symptoms, prevent serious complications, and improve your quality of life. In addition, most people with this disorder live full and active lives.
Types of Nemaline Myopathy
Healthcare providers have divided this disorder into 6 main types. For example:
- Typical congenital nemaline myopathy – It is one of the most common types of this disorder, and it accounts for about 50% of all diagnosed cases.
- Intermediate congenital nemaline myopathy – This type affects about 20% of all cases of NM, and it often causes mild to moderate symptoms.
- Severe congenital nemaline myopathy – This form of NM affects about 16% of cases. Moreover, it may cause severe symptoms, and it is often present at birth.
- Childhood-onset nemaline myopathy – In such cases, the symptoms begin to appear between the ages of 10 and 20. This type of disease negatively affects about 10% of cases.
- Adult-onset nemaline myopathy – This type of the condition accounts for about 4% of all diagnosed cases. People with this type often start to notice symptoms between the ages of 20 and 50.
- Amish nemaline myopathy – This form of nemaline myopathy negatively affects the Amish community. While there are a few cases registered, it is a severe form of the disease that often leads to death in early childhood.
How Common is Nemaline Myopathy?
In general, this condition occurs rarely and affects about 1 out of 50,000 live births. Furthermore, about 1 in every 500 people in the Amish community may develop nemaline myopathy.
Symptoms
While the primary symptoms of this disorder are hypotonia (weak muscle tone), muscle weakness, and lessened or no reflexes, it may also cause other symptoms. Check below some symptoms often noticed in infants:
- Dysarthria (speaking problems)
- Dysphagia (difficulty swallowing)
- Elongated face
- Velopharyngeal dysfunction (nasally speech)
- Dyspnea (shortness of breath)
- Breathing problems during sleep (nocturnal hypoventilation) that often lead to hypercarbia (increased levels of carbon dioxide in the blood)
- Arched roof of the mouth
- Displaced jaw
- Gait disorder (abnormal waddling walk)
In addition, NM may also cause additional symptoms as a person gets older. These include:
- Pectus excavatum (sunken chest)
- Joint contractures (shortening or tightening of the joints)
- Scoliosis
- Abnormal spine rigidity
Immediately contact your healthcare professional if any of the previous symptoms occur.
Causes
This condition is a type of musculoskeletal system disease that is caused by certain genetic changes (mutations). While most people with NM get the abnormal genes from their biological parents, in some cases, a new genetic mutation may occur during conception or pregnancy. Most people with NM have a mutation of the nebulin (NEB) or actin alpha-1 (ACTA1) genes. In general, these are proteins that are a part of the sliding molecular machinery that shortens muscles.
Risk Factors
While this condition may affect anyone, there are some factors that may increase your risk of developing it. For example, a family history of the disease, pregnancy complications, smoking and alcohol drinking during pregnancy, the Amish community, and others. For more information, discuss it with your physician.
What Are The Potential Complications of Nemaline Myopathy?
People with this condition frequently experience complications, especially if they do not get treatment. Check below some complications according to the type of the disease:
Severe Congenital Nemaline Myopathy
- Aspiration pneumonia
- Cardiomyopathy
- Respiratory failure
- Bone fractures
- Arthrogryposis multiplex congenita (this is a condition in which multiple joints become fixed, bent, or straightened)
Adult-onset Nemaline Myopathy
These include:
- Breathing problems
- Heart issues
- Weak neck muscles
- Moderate to severe muscle weakness
Amish Nemaline Myopathy
- Severe hypotonia
- Respiratory failure that requires support (such as mechanical ventilation)
- Muscle atrophy
- Death
The previous lists do not contain all possible complications of NM. However, you can talk with your healthcare professional about measures to reduce the risk or even prevent them. In addition, it is not possible to prevent this condition because it is a genetic disorder that occurs during pregnancy. However, you can perform some genetic tests to make sure you do not have the abnormal genes that cause NM. It is very important to understand the risks of having children with NM.
Diagnosis
Usually, doctors begin the diagnosis of NM with a physical examination to check for abnormalities linked to the disease. They may also ask some questions about your symptoms and medical history to get more information about your disease. However, to confirm or rule out this disorder, doctors often perform a biopsy. During this test, they will take a small sample of the affected tissue for testing under a microscope. Sometimes, physicians perform genetic tests to check for the abnormal genes that cause NM.
Treatment
The treatment goal is to relieve the symptoms and improve your quality of life. Check the most recommended treatments for people with NM below:
- Low-intense exercise to maintain muscle strength
- Massage and physical therapies to improve muscle function
- Speech therapy to address speech issues or nasally speech
- Stretching techniques to improve mobility
- Walking devices, including a cane, crutches, knee braces, splints, or a wheelchair
- Mechanical ventilation, a tracheostomy, or a bilevel positive airway pressure (BiPAP) machine to improve breathing problems
In more severe cases, doctors may also recommend surgery to treat joint contractures or scoliosis and tube feeding (enteral nutrition).
Frequently Asked Questions
Why is it called Amish nemaline myopathy?
This is a type of NM, and it causes weakness and eosinophilic rodlike inclusions in muscle fibers. It is called Amish nemaline myopathy because it occurs among the Old Order Amish.
What are the symptoms of nemaline myopathy?
The most common symptoms include muscle weakness, hypotonia (low muscle tone), and reduced or even a lack of reflexes. However, this condition may cause more severe symptoms. It depends on the type of condition, age, overall health, and other factors.
How rare is nemaline myopathy?
According to some research, there are fewer than 5,000 people with NM in the U.S. In general, it is quite difficult to estimate the exact number of people with this condition. If you have additional questions, ask your healthcare provider.
