In today's wording, the suffix –itis means a disease or inflammation of a specific organ or tissue. In the case of myositis, it is the muscles that are inflamed or diseased.

Myositis can cause muscle diseases known as myopathies. Sometimes, a person may have myositis and not know the underlying cause.

Fast facts on myositis:

  • There are many types and causes, ranging from injury to infection.
  • Diagnosis can be difficult, as many conditions cause symptoms of muscle weakness.
  • Unfortunately, there are no cures for myositis.

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Symptoms associated with inflammation and muscle weakness may include difficulty rising from a seated position and feeling tired after short periods of walking.

Several myositis types exist that cause varying symptoms. However, there are some generalized symptoms associated with muscle weakness and inflammation.

Examples include:

  • difficulty rising from a seated position
  • feeling tired after short periods of standing or walking
  • problems climbing up stairs
  • problems lifting up the arms
  • problems swallowing or breathing
  • unexplained muscle pain or soreness

A person with myositis will also likely have raised levels of the muscle enzymes CPK or aldolase.

Some types of myositis cause specific symptoms, such as a telltale skin rash or weakness in specific areas of the body.

However, muscle weakness, fatigue, and sometimes pain or discomfort are all symptoms with most myositis types.

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The presence of viruses such as the cold and flu virus, may be a common cause of myositis.

Myositis can have a variety of underlying causes, although sometimes doctors cannot identify a reason. Examples of more common myositis causes include:

  • autoimmune disorder, such as lupus or rheumatoid arthritis
  • infection
  • medications, including statins prescribed to lower cholesterol
  • muscle injury
  • presence of viruses in the body, including the cold and flu virus of the human immunodeficiency virus (HIV)
  • use of illegal drugs, such as cocaine

Sometimes the underlying causes of myositis are more apparent. This is the case when they are medication or drug-related. However, there are many myositis cases of unidentified cause, when the condition is known as idiopathic myositis.

Some of the most common types of myositis include the following:

Dermatomyositis

This condition causes a visible, patchy, red or purple skin rash. A person will also experience muscle weakness and occasionally pain related to the condition. Women are more likely than men to experience this myositis type.

Drug-induced myositis

This condition is most commonly due to inflammation that is a side effect of medications. Examples of medicines known to cause myositis include statins, such as lovastatin or zidovudine (Retrovir), which doctors prescribe to treat HIV and AIDS.

Inclusion-body myositis

Men older than 50 years of age are more affected by this myositis type. People with this condition experience gradual muscle weakening. They may also experience difficulty swallowing, a problem known as dysphagia.

Juvenile myositis

This condition occurs in those younger than 18 years of age and typically affects girls. Juvenile dermatomyositis can cause a purple or red skin rash, often over the eyelids, a weak voice, or difficulty swallowing.

Most people with this condition will also experience an inflammation of the blood vessels, which is known as vasculitis. Some children will have muscle pain, while others will have muscle weakness, especially in the stomach, neck, upper arms, and legs.

Infective myositis

This myositis type is common in people with a viral infection, especially the flu. However, a person can also experience infectious myositis due to trichinosis, a parasite that is present in undercooked or uncooked meat. Bacteria, especially the staph bacteria, can also cause myositis.

Myositis ossificans

This condition most commonly results from an injury, such as a significant bruise. The condition causes a hard, bony lump to form inside the affected muscle.

Polymyositis

This condition is also more common in women than men. People with polymyositis have gradual muscle weakness that starts at a person's core and can spread outward. Cancers and autoimmune disorders can cause polymyositis.

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A doctor may recommend a blood test to help diagnose myositis.

A doctor will start by asking a person about their health history and symptoms. Questions may include what time of the day the symptoms usually occur, if anything improves symptoms and if anything makes them worse.

A doctor may then recommend diagnostic tests to determine if myositis or another condition is the cause.

Examples of these tests include:

  • Blood testing: Blood testing can measure the presence of muscle enzymes, such as CPK, and the presence of antibodies associated with autoimmune disorders.
  • Imaging testing to identify areas of muscle abnormality: Myositis ossificans is an imaging test that is often used.
  • An electromyogram: This test uses special monitoring to determine a muscle's electrical activity.
  • Biopsy: A muscle biopsy can identify inflamed areas.

A doctor may recommend further testing, as necessary, based on the myositis type.

Doctors can use treatment methods to help a person manage the symptoms of their disease.

A doctor may first prescribe medications known as corticosteroids. These drugs reduce inflammation in the body, which can help some of the most immediate muscle symptoms.

Antibiotics

Sometimes treatment for myositis addresses the underlying cause. For example, doctors may treat bacterial causes of myositis with antibiotics.

If a person's myositis is related to an autoimmune disorder, a doctor may prescribe disease-modifying anti-rheumatic drugs (DMARDs).

Examples of these medications include azathioprine and methotrexate.

Home treatments

A person can also try some at-home treatments to find relief from myositis. Exercise if one example.

Moving the muscles regularly and engaging in resistance exercises can help to build strength. Stretching can also enhance the range of motion and flexibility.

A person with myositis may work with a physical therapist, a professional who specializes in exercises and stretches for recovery.

Sometimes myositis is a short-term problem that will resolve. At other times, it is a chronic condition that can result in muscle wasting that affects a person's daily life. This is true for polymyositis and dermatomyositis, which tend to be long-term conditions. Conditions, such as infectious myositis, usually resolve when a person's overall health improves.