Myopathy Muscle Disease
Myopathy is the medical term for a muscular disorder; the plural is myopathies. The condition affects skeletal muscles, those that are connected to bones. Examples are the quadriceps muscle in the thigh and the biceps in the arm. The primary symptom of myopathy is muscle weakness.
Myopathies can be caused by genetic defects or endocrine or metabolic disorders. Other causes are infection, muscle injury, medication, problems with electrolyte levels and thyroid disease. The cause of inflammatory myopathies (see below) is not known.
Some myopathies are resistant to treatment, while others are more treatable. Myopathy can be inherited (such as the familiar muscular dystrophies) or acquired (such as common muscle cramps). In severe cases the muscle weakness can lead to respiratory failure and death.
Myopathies are categorized as follows:
- Congenital. Developmental delays in motor skills; skeletal and facial abnormalities sometimes evident at birth. Includes central core disease.
- Muscular. Progressive weakness in voluntary muscles; sometimes evident at birth.
- Mitochondrial. Caused by genetic abnormalities in mitochondria, which are the structures in cells that control energy. Includes Kearns-Sayre syndrome, MELAS and MERRF.
- Glycogen storage diseases of muscle. Caused by mutations in genes controlling enzymes that metabolize blood sugar. Includes Pompe’s, Andersen’s and Cori’s diseases.
- Myoglobinurias. Caused by disorders in the metabolism of a fuel (myoglobin) necessary for muscle activity. Includes McArdle, Tarui and DiMauro diseases.
- Dermatomyositis. An inflammatory condition of skin and muscle; causes a rash and in some cases cough/shortness of breath.
- Myositis ossificans. Characterized by bone growing in muscle tissue.
- Familial periodic paralysis. Episodes of weakness in the arms and legs.
- Polymyositis, inclusion body myositis (IBM) and others. These are inflammatory myopathies affecting skeletal muscle.
- Neuromyotonia. Characterized by alternating episodes of twitching and stiffness.
- Stiff-man syndrome: Episodes of rigidity and reflex spasms.
- Common muscle cramps and stiffness.
- Tetany. Characterized by prlonged spasms of the arms and legs.
If you believe you may have one of these conditions make an appointment to see your Wellstar neurologist to ensure effective diagnosis and treatment. Our neuroscience team is expert in helping patients diagnose, treat and live with myopathy.
Most myopathies result in weakening and atrophy of the muscles, especially the proximal muscles—those closest to the center of the body. The distal muscles, those farther away from the center such as in the hands or feet, are not typically affected. Individuals with myopathy often have difficulty performing activities of daily living (like dressing and bathing). Muscle pain and tenderness are rare.
Specific symptoms differ according to the type of myopathy involved. In addition to muscle weakness, many patients experience cramps and fatigue with exertion. They may have difficulty getting out of a chair, climbing stairs, changing a light bulb or washing/combing their hair. In some metabolic myopathies patients may experience tea- or dark-colored urine.
The onset and nature of symptoms can be important clues that help your physician make an accurate diagnosis. For example, if weakness progresses over hours the diagnosis may be episodic paralysis. However, if symptoms develop over a period of weeks, the condition may by polymyositis, a myopathy that can caused by medications or endocrine problems like an overly active, or under-active thyroid.
Some myopathies, including some muscular dystrophy conditions, are inherited. Other risk factors for myopathy include:
- Autoimmune disorders (myasthenia gravis, scleroderma, thyroiditis)
- Endocrine disorders (Addison disease, Cushing syndrome, hypothyroidism, hyperthyroidism)
- Exposure to toxins including insecticides and flame-retardant chemicals
- Vitamin deficiency
- Use of medications including antihistamines and long-term corticosteroids
- Metabolic disorders (glycogen and lipid storage conditions)
There are no known ways to prevent myopathy. Muscle inflammation may be caused by an allergic reaction, exposure to a toxic substance or medicine, another disease such as cancer or rheumatic conditions, or a virus or other infectious agent. The chronic inflammatory myopathies are idiopathic, meaning they have no known cause. They are thought to be autoimmune disorders, in which the body’s white blood cells (that normally fight disease) attack blood vessels, normal muscle fibers, and connective tissue in organs, bones, and joints.
During an office visit your Wellstar neurologist will conduct a physical exam as well as a neurological exam. The doctor will ask questions about family medical history and will want to know about your symptoms including the type and pattern of muscle weakness. He or she may also ask about drug use, chemical exposures and exercise intolerance.
Tools and Tests
Your doctor may use various lab tests to more precisely diagnose myopathy or rule it out. The most definitive diagnostic test is a muscle biopsy, which is performed on an outpatient basis. A small portion of muscle is removed for examination. This test can reveal many abnormalities and help diagnose myopathy and its type.
- Blood tests to check for the level of CK (creatine kinase) an enzyme that leaks from muscle fibers when the fibers are damaged.
- Blood tests for certain antibodies. These are proteins produced by the immune system in myositis and other immune disorders.
- Electromyogram, a test that involves the insertion of tiny needles into the muscles to test their electrical activity.
- Nerve conduction velocity test to measure the speed at which a nerve impulse travels, and the strength of that impulse.
- Urine test
- Thyroid function test
- Magnetic resonance imaging (MRI) to assess complications or rule out neurologic disease.
Options include medication, physical therapy, exercise, heat therapy (including microwave and ultrasound), orthotics and assistive devices and rest. Inflammatory myopathies that are caused by medicines, a virus or other infectious agents, or exposure to a toxic substance usually abate when the harmful substance is removed or the infection is treated. If left untreated, inflammatory myopathy can cause permanent disability.
Polymyositis and dermatomyositis are first treated with high doses of corticosteroid drug. This is most often given as an oral medication but can be delivered intravenously. Immunosuppressant drugs, such as azathioprine and methotrexate, may reduce inflammation in individuals who do not respond well to prednisone. Periodic treatment using intravenous immunoglobulin can increase the chance for recovery in individuals with dermatomyositis or polymyositis. Other immunosuppressive agents that may treat the inflammation associated with dermatomyositis and polymyositis include cyclosporine A, cyclophosphamide, and tacrolimus.
Physical therapy is usually recommended to prevent muscle atrophy and to regain muscle strength and range of motion. Bed rest for an extended period of time should be avoided, as people may develop muscle atrophy, decreased muscle function, and joint contractures. A low-sodium diet may help to counter edema and cardiovascular complications.
Many individuals with dermatomyositis may need a topical ointment (such as topical corticosteroids or tacrolimus or pimecrolimus) or additional treatment for their skin disorder. A high-protection sunscreen and protective clothing should be worn by all affected individuals, particularly those who are sensitive to light. Surgery may be required to remove calcium deposits that cause nerve pain and recurrent infections.
The goal of other strategies, known as supportive care, is to preserve muscle activity, allow for maximal functioning and extend life expectancy. Supportive treatments include:
- Medications including immunosuppressives that suppress the strength of the body’s immune systems.
- Orthopedic treatments
- Physical, occupational or speech therapy
- Bracing to support weakened muscles
- Physical therapy to improve mobility and other supportive therapies focused on individual symptoms.
Wellstar advocates a team approach for the best treatment of many hereditary myopathies. In addition to a neurologist, team members may include a pulmonologist, cardiologist, orthopedic surgeon, counselors, physiatrist, and physical, occupational or speech therapist.
Your doctor will discuss the need for therapy depending on the muscles affected. Wellstar’s expert therapists offer comprehensive service at a number of convenient locations.
Ongoing Care for Myopathy
Many people with myopathy live with few limitations. For others the effects of the condition can be more disabling, including mobility and breathing difficulty. In infants, myopathy can lead to breathing, feeding and swallowing problems, which can lead to respiratory complications or failure.
Wellstar offers smoking cessation programs that educate people about smoking risks, encourage behavior modification to help minimize smoking urges and offer numerous coping strategies.