Myopathies are disorders of the muscles that cause them to function less effectively. Myopathies can be inherited or acquired, and the symptoms may be present from birth or develop later on.
Skeletal muscles consist of fibers made of protein. When a muscle contracts, the fibers slide over one another, shortening the muscle. This moves our limbs, and myopathies can affect this movement.
Below, we explore different types of myopathies and their symptoms. We also look into the treatment plans and outlook for people with these disorders.
Doctors classify myopathies in various ways.
People are born with these disorders.
These myopathies are similar to muscular dystrophy, though muscular dystrophy refers to a group of genetic disorders that lead to a progressive loss of muscle fibers.
In someone with a myopathy, the muscles do not function correctly. In someone with muscular dystrophy, the muscles degenerate and become progressively weaker.
Central core myopathy is one of the most common congenital myopathies. Mutations in the RYR1 gene cause this disorder. They affect the way that muscles contract, causing muscle weakness.
These pass from parents to children.
These develop due to an illness or imbalance in the body.
Genetic abnormalities cause inherited myopathies.
Some result from irregularities in the mitochondria of cells, and these are called mitochondrial myopathies. They may stem from genetic mutations or occur due a spontaneous gene mutation, in someone without a family history of the disorder.
Another type is metabolic myopathy, which results from irregularities in a muscle’s metabolic pathway. Metabolic myopathy affects the genes that code for the enzymes responsible for muscle function.
Acquired myopathies, on the other hand, do not have genetic causes. Some examples include:
- Autoimmune or inflammatory myopathy: This involves the body attacking itself, interfering with muscle function. It may be linked with an autoimmune disease, such as lupus, rheumatoid arthritis, or scleroderma.
- Infectious myopathy: This occurs when an infection prevents regular muscle function.
- Endocrine myopathy: This occurs when hormone imbalances interfere with regular muscle activity.
- Toxic myopathy: This involves medication, an illegal drug, or a large quantity of alcohol impairing muscle function.
An electrolyte imbalance can also interfere with a muscle’s ability to contract and relax as it should.
This type of disorder may also affect the respiratory muscles, which can lead to trouble breathing. And a myopathy may prevent the muscles from adequately supporting the bones, leading to bone deformation.
In addition, some congenital myopathies can lead to a delay in a child developing gross motor skills, which are large movements. These are made with the entire body or just the arms, legs, or feet, such as crawling or running.
More specifically, mitochondrial myopathy
Other symptoms of myopathy may include:
- muscle cramps or spasms
- muscle pain
- low energy and fatigue
- exercise intolerance
- skin rashes
Over time, people may also experience muscle wasting, which is a loss of muscle mass.
Learn more about muscle wasting here.
Some myopathy symptoms are present at birth, and others develop later in life. It is important that a doctor rules out other possible causes of the symptoms, such as myasthenia gravis.
A primary care doctor usually refers a person with myopathy symptoms to a neurologist or rheumatologist.
The process starts with the doctor taking a full medical history. They then conduct a physical evaluation. This may include testing muscle tenderness, strength, balance, reflexes, and sensation.
They may need additional tests, including blood, metabolic, thyroid and other endocrine tests. The doctor may also request genetic tests, a muscle biopsy, and tests for specific muscle autoantibodies.
Blood tests can indicate:
- electrolyte balances
- inflammation levels
- autoimmune activity
- the presence of muscle breakdown
The doctor may also suggest an electromyography test to assess muscle function. And imaging tests, such as MRI and ultrasound, can help identify the location of the affected muscles and the severity of the disorder.
Treatment options for myopathy depend on the type and severity.
To treat autoimmune myopathies, a doctor may prescribe immunosuppressive drugs, such as glucocorticoids, mycophenolate, rituximab, or intravenous immune globulin.
Glucocorticoids are a type of steroid hormone. They work by suppressing many immune pathways responsible for causing inflammation in the body. Glucocorticoids work quickly, but due to the risk of side effects, a doctor quickly minimizes the steroid dosage and adds other medications to the treatment plan.
For some acquired myopathies, treating the cause may reduce the symptoms. For example, rebalancing electrolyte levels in the body may help with muscle fatigue and cramps. If an underactive thyroid is the cause of the myopathy, boosting thyroid hormone levels may have the same effect.
For a person with toxic myopathy, stopping exposure to the problematic drug may
Gene therapy for congenital myopathy has shown some success in
Meanwhile, both acquired and inherited types of myopathy require supportive therapy. For example, physical therapy and limited bracing
Complementary therapies may also help. These might include:
- gentle acupressure
- massage therapy
It is important not to overly exert the muscle when there is inflammation. But stretching and other exercises that focus on maintaining the range of motion can be key.
Over-the-counter nonsteroidal anti-inflammatory drugs, known as NSAIDs, may help relieve any associated pain. But discuss these with a healthcare professional first, to prevent drug interactions and side effects. Ibuprofen (Advil, Motrin) is one example of an NSAID.
The outlook for people with myopathy depends on the type and severity of the disease.
Some people few symptoms and a regular lifespan, while others have disorders that worsen progressively and significantly limit aspects of their lives.
Over time, myopathies may become disabling or life threatening. It is important to work with a doctor to develop and adapt a treatment plan.
Myopathies are a group of muscle disorders, and the main symptom is muscle weakness.
People may inherit or acquire these disorders. If a person acquires them, medication, inflammation, or an electrolyte imbalance may be responsible.
The best approach to treatment and a person’s outlook depend on the type and severity of the myopathy.