Myositis is a rare autoimmune disease that causes muscles to become swollen and inflamed. This disorder affects the voluntary muscles of the body that consciously control movement. Myositis may develop slowly over time and can range in severity from mild to severe. Myositis causes progressive weakness and inflammation in muscles throughout the body and can affect adults and children.

Types of Myositis

Different forms of myositis may have varying symptoms and affect different parts of the body.


Polymyositis affects many muscles of the body. This condition affects women more than men with symptoms that may include muscle pain and weakness, difficulty swallowing and joint pain and inflammation.


Dermatomyositis is a form of myositis that causes damage to the muscle fibers and the skin. In addition to muscle weakness and pain, a common symptom of dermatomyositis is a purplish rash on the face and eyelids and other parts of the body.

Inclusion Body Myositis

Inclusion body myositis is an inflammatory muscle disorder that causes progressive weakness and inflammation in muscles throughout the body. As muscle weakness progresses over time, individuals may experience difficulty swallowing, frequent falls and weakness in the extremities. Inclusion body myositis commonly affects individuals over the age of 50 and is more prevalent in men than women.

Juvenile Myositis

Juvenile myositis is a form of myositis that affects children. Symptoms include fatigue, muscle weakness and pain, and a skin rash. Children with juvenile myositis may also have difficulty swallowing and breathing, and the heart may be affected.

Although some symptoms may vary, all types of myositis are characterized by chronic muscle inflammation accompanied by muscle weakness.

Causes of Myositis

The exact cause of myositis is unknown. However, research suggests that it is an autoimmune disorder, where the body's immune system destroys healthy tissue and muscle in the body, causing inflammation. This autoimmune disorder may be triggered by a virus that in turn causes different forms of myositis.

Symptoms of Myositis

The main symptom of myositis is muscle inflammation and weakness. Other symptoms may vary based on the specific type of myositis and may include:

  • Muscle pain
  • Fatigue
  • Skin rash
  • Difficulty swallowing
  • Shortness of breath
  • Joint pain and tenderness

The muscle pain and weakness caused by myositis may make it difficult to perform normal activities such as rising from a seated position or even walking. Many individuals suffering from myositis may need the assistance of a cane, walker or other assistive device to increase mobility.

Diagnosis of Myositis

Myositis may be diagnosed after an evaluation of the patient's medical history and a full physical examination. Additional tests may include:

  • Blood tests
  • Electromyogram
  • MRI scan
  • Nerve conduction velocity test

A muscle biopsy may also be performed to examine the strength and health of the affected muscles. These tests may also be used to rule out any underlying disorders that may mimic the symptoms of myositis.

Treatment of Myositis

There is no cure currently available for myositis and and effective treatment approaches can vary based on the type of myositis that the patient is suffering from. The methods of treatment are not always completely successful. Myositis is sometimes treated with drugs that suppress the immune system, however, these treatments are not always effective. Corticosteroid medication may also be prescribed to control inflammation, ease pain, and increase muscle strength. Intravenous immunoglobulin therapy may be administered to patients that are experiencing swallowing problems. Physical therapy may also be effective in increasing mobility and improving physical activity and is an important part of a treatment plan.

Additional Resources