Myopathy is a general term referring to any disease that affects the muscles that control voluntary movement in the body. Patients experience muscle weakness due to a dysfunction of the muscle fibers. Some myopathies are genetic and can be passed from parent to child. Others are acquired later in life and can be due to autoimmune disease, known as myositis, metabolic disorders or other causes.
There are several different types of genetic myopathies, most of which have similar symptoms. These include:
- Muscle weakness
- Motor delay
- Respiratory impairment
- Bulbar muscle dysfunction (malfunction of the muscles responsible for swallowing and speech)
Bulbar muscle dysfunctions can be especially apparent in congenital myopathies (those present from birth), and can result in severe impairments to swallowing and speech abilities. Congenital myopathies also are characterized by developmental motor delays and, at times, facial or skeletal abnormalities.
Acquired myopathies may have symptoms similar to those of genetic myopathies and also may include:
- Muscle weakness
- Muscle soreness (myalgias)
- Muscle wasting around the shoulders and hips
Causes and Risk Factors
Patients who have a blood relative with a genetic myopathy have an increased risk for developing the condition. Depending on how the myopathy is inherited, men can be at greater risk than women of developing the condition. Myopathies carried on the X chromosome affect more men than women, while those carried on chromosomes other than the sex chromosome affect both men and women equally.
Patients may be at increased risk of developing acquired myopathy if they have an autoimmune disorder, metabolic or endocrine disorder, are on certain drugs or are exposed to certain toxins.
The patient’s physician may use a variety of tests to determine the specific myopathy. These can include:
- A physical exam
- Muscle strength tests
- Electromyography (EMG)
- Magnetic resonance imaging (MRI)
- Genetic tests
- A muscle biopsy
The goal in determining the specific myopathy of each patient is to enable the development of a personalized treatment plan.
While there is no cure for genetic myopathy, many different treatment options are available to manage the symptoms. Treatments for both genetic and endocrine myopathy are most effective when the disease is diagnosed early and a comprehensive treatment plan is overseen by a knowledgeable medical team, such as those at Cedars-Sinai’s Neuromuscular Disorders Program.
For acquired myopathies due to the immune system, such as dermatomyositis and polymyositis, medications that work to reduce the body’s immune response and decrease inflammation, such as corticosteroids or other immunosuppressants, can help manage some symptoms. Physical therapy, supportive devices such as braces, and sometimes surgery may also be used as treatment tools.
Treatment of metabolic, toxic and endocrine-related myopathy generally focuses on the underlying cause of the condition. Medication or surgery may be used to address the symptoms.