3 Causes of Myopathy

Myopathy is a disease of the skeletal muscles (muscles that connect to bones) that can lead to weakness, fatigue, and tissue loss. Severe cases can impair organ function, create severe health complications, and even cause respiratory failure.

At Memphis Neurology, our team of board-certified, expert neurologists diagnoses and treats all manner of myopathies at our offices in Southaven, Mississippi, and Germantown, Tennessee. Here’s what you need to know about the three main causes of myopathy and how we treat them.

3 causes of myopathy

While myopathy causes are sometimes classified as due to 1) genetics, 2) autoimmune diseases, and 3) endocrine system disorders, perhaps a more functional approach is to divide the causes into two big categories: inherited and acquired.

Inherited myopathies are conditions you’re born with, often stemming from an abnormal gene or a genetic mutation inherited from a parent. Some of the manifestations include:

Mitochondrial myopathies

Mitochondria are the energy-producing organelles found inside your cells, and when they can’t function properly, they affect the ability of the muscles to contract. Mitochondrial myopathies lead to muscle weakness, but they produce a variety of other symptoms, too, since they also affect organ systems like your heart, brain, and gastrointestinal tract. You can inherit the gene mutation, or the mutation can arise spontaneously.

Mitochondrial disorders affect about 1 in 5,000 people.

Metabolic myopathies

When defects occur in genes that code for enzymes needed for normal muscle function and movement, they can cause metabolic myopathies. These often present as exercise intolerance, muscle pains in your shoulders and thighs that stem from activity, or non-traumatic rhabdomyolysis, a muscle fiber condition. You may experience episodes of weakness that come and go, with normal strength at other times.

Muscular dystrophies

Muscular dystrophies are severe cases of myopathy, characterized by progressive degeneration of muscle tissue arising from abnormal or insufficient structural support proteins. All forms of dystrophy involve loss of function in the arms and/or legs to varying degrees, and some affect the muscles of your eyes or face.

Duchenne’s and Becker’s muscular dystrophies are the most common types, with 7 per 100,000 people worldwide affected, primarily males.

Acquired myopathies develop sometime later in life. They can be due to other medical disorders, exposure to certain toxins or medications, infections, or electrolyte imbalances. Some of the more common include:

Autoimmune/inflammatory myopathy

Autoimmune diseases are conditions where your immune system mistakenly attacks your own body’s cells, which can lead to problems with muscle function. Some examples include rheumatoid and psoriatic arthritis, systemic lupus erythematosus (SLE), and inflammatory bowel disease (IBD).

The goal of treatment is to decrease inflammation and the autoimmune response. Immunomodulatory/immunosuppressant drugs and corticosteroids are the most common medications used.

Endocrine myopathy

When hormones interfere with muscle function, you develop endocrine myopathy. Some common culprits include:

• Thyroid: both low and high thyroid hormone levels can interfere with muscle function
• Parathyroid: hyperparathyroidism increases calcium levels, which affects muscles
• Adrenal: Addison’s disease and Cushing syndrome

Treatment of the underlying condition usually helps the myopathy.

Infectious myopathies

Infectious myopathies result from infections that affect muscle function. These include:

• Viral infections: HIV, influenza, Epstein-Barr
• Bacterial pyomyositis
• Lyme disease
• Parasitic infections: trichinosis, toxoplasmosis, cysticercosis
• Fungal infections: Candida, Coccidiomycosis

Antibiotics, antivirals, and antifungals target the underlying sources of infection, resolving muscle problems.

More about treating myopathy

Most treatments include a combination of physical therapy, occupational therapy, and some form of exercise, which can strengthen muscles and reduce symptoms. Most acquired myopathies can be well controlled with these and the appropriate treatment of the underlying condition responsible for the myopathy.

Some inherited myopathies, such as Duchenne muscular dystrophy and Pompe disease, have specific treatments that halt the progression of the disease, but most inherited myopathies don’t. Treatment is largely based on symptom control, with the addition of physical therapy and exercise. Clinical trials, including those related to gene therapy, are ongoing.

If you’re experiencing muscle weakness, especially in the arms and legs, you may be dealing with myopathy. To get an accurate diagnosis and effective treatment, come into Memphis Neurology for an evaluation by one of our neurologists. Give us a call at either of our locations, or book online with us today.