Myopathy Symptoms, Causes, and Treatment

Myopathy refers to diseases of skeletal muscles (muscles connected to bone). The condition can be acute (meaning sudden, severe, and short-lasting) or chronic (persistent, recurrent, and often progressive). Symptoms of myopathy include muscle weakness, stiffness, and cramps.

There are many different causes of myopathy. It may be due to a congenital condition you are born with or something that develops in later life due to an infection, injury, medications, or diseases like diabetes, hypothyroidism, lupus, or rheumatoid arthritis.

This article describes the causes and symptoms of myopathy, including how myopathic diseases and disorders are diagnosed and treated.

Definition

Myopathy is a general term referring to a disease of skeletal muscle. With myopathy, these muscles work less effectively than they should, causing weakness and other motor symptoms. Myopahthy can occur when the muscles do not develop properly, become damaged, or lack certain structural components needed to function normally.

A muscle is composed of bundles of fibers called myofibers that work in coordination to contract (shorten) a muscle. When the fiber bundles are damaged or defective, myopathy can occur.

There are many different causes of myopathy. Some are progressive and worsen over time, while others are fairly stable or short-lived. Several myopathies are inherited (passed from parents to children), and many are not.

Causes and Types of Myopathy

Myopathy can be broadly categorized as being either inherited or acquired. People with inherited myopathies tend to experience chronic symptoms, while those with acquired myopathies may have acute or chronic symptoms depending on the underlying cause.

Inherited

Inherited myopathies can sometimes be congenital (meaning something you are born with) or be caused by a genetic condition that predisposes you to myopathy in later life.

Inherited myopathies include:

• Central core myopathy: This is a type of congenital myopathy that affects the central core of muscles, causing weakness and bone problems. The severity of the disease varies, causing profound weakness among some people and only mild weakness in others.
• Muscular dystrophy: This is a group of congenital diseases caused by the degeneration of muscle fibers. Muscular dystrophies are typically progressive, leading to an inability to walk and eventually death (usually due to respiratory weakness).
• Mitochondrial myopathy: This is a disease caused by a defect in the energy-producing part of cells, called the mitochondria. There are several types of mitochondrial myopathy that not only affect not only skeletal muscles but smooth (involuntary) muscles of the digestive tract.
• Metabolic myopathy: This group of genetic diseases that interfere with metabolism (the conversion of calories to energy). Certain genetic mutations can cause the inadequate production of enzymes needed to fuel metabolism in muscles.
  
• Nemaline myopathy: This is a group of congenital disorders characterized by the presence of a harmful structure in muscles called nemaline rods. Nemaline myopathy is often associated with respiratory muscle weakness.
• Myotonia: This is a group of diseases that cause prolonged muscle contractions after a muscle is flexed (such as a grip that can't be released). This includes myotonic dystrophy which generally improves with movement and myotonia congenita which does not.
• Brody myopathy: This is a rare genetic disorder that makes it difficult to relax muscles after exercise. Symptoms like stiffness and cramps are heightened by exercise and tend to get worse as you get older.
• Familial periodic paralysis: This is a rare genetic condition that causes temporary muscle weakness or paralysis of the arms and legs. It can be set off by triggers such as cold, heat, stress, excitement, exercising, not eating, or eating high-carbohydrate foods.

Acquired

Myopathy can also be caused by a variety of illnesses or conditions. Some are systemic diseases that affect the body as a whole. Others are caused by substances that affect normal muscle function.

Commonly acquired myopathies include:

• Autoimmune myopathy: This occurs when the body attacks its own cells and tissues, causing inflammatory muscle injury or degeneration. These include polymyositis, dermatomyositis, sarcoidosis, lupus, and rheumatoid arthritis.
• Toxic myopathy: This occurs when a toxin or medication injures a muscle or muscle nerves. Examples include alcohol, statins, fibrates, iodine, niacin, steroids, propofol, amiodarone, colchicine, chloroquine, omeprazole, tryptophan, and certain antivirals.
  
• Endocrine myopathy: This occurs when a disorder of the hormonal system interferes with muscle function. The most common causes include thyroid disease, adrenal diseases, and diabetes.
• Infectious myopathy: This may happen when an infection prevents the muscles from functioning properly. Causes include viral infections like HIV, influenza, and Epstein-Barr and bacterial infections like Staphylococcus aureus or Lyme disease.
• Nutritional myopathy: Deficiencies of vitamin D and vitamin B12 cause can myopathy. Electrolyte problems, such as excessively high or low potassium levels, can also interfere with muscle function.
• Myositis ossificans: This occurs when calcium deposits form in muscles following an injury. It most often affects the thigh or upper arm. Myositis ossificans symptoms include aching pain and a reduced range of motion of the affected muscle.
• Rhabdomyolysis: This a condition in which damaged skeletal muscle breaks down rapidly causing muscle pains, weakness, and irregular heartbeat. Rhabdomyolysis is usually caused by a crush injury, strenuous exercise, medications, or substance abuse.

What Are the Symptoms of Myopathy?

Myopathy is characterized by muscle weakness. With that said, the symptoms can vary by the underlying cause and may not only involve skeletal muscles but other organ systems as well.

Some common symptoms of myopathy include:

• Muscle weakness or fatigue
• Muscle pain
• Muscle stiffness or clenching
• Muscle cramps or twitches
• Problems standing or walking
• Trouble breathing, especially when exercising
  
• Swallowing problems
• Muscle thinning (atrophy)

What Does Myopathy Feel Like?

Myopathy is a broad term that can be ascribed to any number of abnormalities affecting movement, motor function, and coordination in adults or children.

If you have myopathy, you might have:

• Trouble getting out of a chair or climbing stairs
• Difficulty performing personal care tasks, such as bathing, dressing, or combing your hair
• Problems with basic motor skills, like changing a lightbulb, opening and closing food containers, or turning handles or doorknobs
• Loss of fine motor skills, such as threading a needle, writing legibly, using a keyboard, or playing a musical instrument
• Trouble controlling muscles involved with speech or swallowing, leading to slurring or choking

In children, myopathy may present with:

• Problems forming word sounds correctly
• Difficulty with gross movements, such as holding up their head, crawling, or walking
• Slow development of motor skills compared to other kids, such as grasping utensils, using scissors, or stacking blocks
• An inability to keep up with kids during playtime, such as playing tag, tether ball, hopscotch, or dodgeball
  

Diagnosis

It can take time to diagnose the underlying cause of myopathy. Depending on the nature of your symptoms, you may be referred to a neurologist or a rheumatologist for evaluation.

The diagnosis will typically start with a review of your medical history and a physical exam to evaluate your reflexes, muscle strength, balance, and sensations.

Other tests may be ordered to narrow the possible causes, including:

• Creatine kinase (CK): This is a blood test that measures an enzyme in muscles that increase if muscles break down abnormally or excessively.
• Blood electrolyte: This blood test checks for electrolyte imbalances, including sodium, magnesium, potassium, calcium, and phosphorus.
• Antinuclear antibodies (ANA) and rheumatoid factor (RF): These blood tests can help detect autoimmune diseases.
• Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP): These blood tests detect general inflammation caused by infections or autoimmune diseases.
• Genetic testing: There are several that can diagnose specific genetic or congenital diseases.
• Endocrine testing: An example includes thyroid hormone blood tests to detect thyroid disease.
• Electromyography (EMG): This needle-like device measures the electrical activity of muscle nerves to assess the level of impairment or injury.
• Magnetic resonance imaging (MRI): This imaging test uses powerful magnetic and radio waves to visualize soft tissues like muscles.
• Muscle biopsy: This is the surgical removal of a small sample of muscle tissue for evaluation in the lab.

Treatment

The treatment of myopathy varies by its underlying cause. Most treatments include some form of physical therapy, exercise, or occupational therapy.

Among the general treatment approaches:

• Inherited myopathies generally don't have a specific treatment plan. In most cases, the focus is placed on the management of symptoms. Certain types of muscular dystrophy can be treated with medications.
  
• Autoimmune myopathies involve drugs that decrease inflammation and your body’s abnormal immune response. This may involve corticosteroids like prednisone or immunosuppressants like methotrexate, cyclosporine, tacrolimus, and azathioprine.
• Toxic myopathies are treated by stopping the offending agent whether it be alcohol or medications.
• Endocrine myopathies involve managing or treating the hormonal condition. An example is treating hypothyroidism (low thyroid function) with a synthetic hormone called Synthroid (levothyroxine).
• Infectious myopathies involve managing or treating the infection whether it be bacterial, viral, fungal, or parasitic.
• Nutritional myopathies are usually improved by treating vitamin deficiencies or electrolyte imbalances with diet and/or supplements.

How Do I Take Care of Myself?

If you have been diagnosed with chronic myopathy, it is important to maintain a healthy lifestyle and make adjustments to accommodate for any limitations you may have.

These may include:

• Participating in physical, occupational, or speech therapy
• Taking your medications as prescribed without missing doses
• Staying active with the appropriate exercise plan as directed by your healthcare provider
• Eating a healthy, well-balanced diet with a variety of fruits, vegetables, lean protein, and whole grains
• Achieving and maintaining a healthy weight under the guidance of a healthcare provider or nutritionist if needed
• Eating soft, semi-soft, or pureed food if you have trouble swallowing
• Using a mobility device, like a cane or walker, that not only helps keep you stable but encourages you to move rather than sit
  

Prognosis

Congenital myopathy tends to worsen or stabilize over time but generally does not improve. Myopathies that are not congenital (such as infectious, metabolic, autoimmune, or toxic myopathies) may improve once the underlying condition is controlled.

If you have a chronic, progressive form of myopathy, it is important to eat correctly, exercise, maintain your ideal weight, and engage in physical therapy if symptoms are severe. Smoking should also be stopped.

Myopathy is not a common condition. However, many individuals diagnosed with myopathy are able to maintain productive lives with a consistent, holistic treatment plan.