Myopathy

Overview

The term “myopathy” describes a group of diseases of skeletal muscle which are not caused by nerve disorders. Myopathies are usually degenerative, and cause the skeletal muscles to become weak or wasted.

Symptoms

The effects of myopathy are typically mild and transitory. Symptoms include muscle weakness and movement problems. Symptoms may cause patients to become wheelchair dependent in rare cases.

Muscular dystrophy is a severe form of myopathy which can have far more serious symptoms. Follow the link to learn more about muscular dystrophy.

Causes

There are many different types of myopathies. Some are inherited and caused by a genetic defect. Myopathies may also be caused by inflammatory response, or endocrine problems. Other possible causes include:
  • drug side effects
  • chemical poisoning
  • chronic disorder of the immune system

Risk Factors

Some of the risk factors for myopathy include:
  • Autoimmune disorders such as scleroderma, thyroiditis
  • Endocrine disorders including Cushing syndrome, hypothyroidism, hyperthyroidism, or Addison disease
  • Metabolic disorders
  • Exposure to toxins such as herbicides or insecticides
  • Infection such as HIV or Lyme disease
  • Vitamin D deficiency, or vitamin E or A toxicity
  • Medications (especially lipid-lowering statins, some antihistamines; long-term corticosteroid use)

Diagnosis

The diagnosis comes from clinical history of weakness frequently accompanied by pain. A doctor may also order blood work or get an electrodiagnostic study, also known as an EMG.

Complications

Most people who develop a myopathy have transient weakness and pain that gets better either on its own, with elimination of the drug or toxin, or with treatment. For some, myopathy can progress to severe and prolonged weakness.

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