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Myositis is a rare group of diseases characterized by inflamed muscles, which can cause prolonged muscle fatigue and weakness.

The group includes the autoimmune disorders juvenile myositis, dermatomyositis and polymyositis, as well as inclusion body myositis (IBM). These diseases, sometimes referred to as inflammatory myopathies, can affect the internal organs, skin and multiple muscle groups of patients.


While each myositis condition has its own unique characteristics and treatments, all of them involve chronic muscle inflammation. This inflammation usually results in muscle fatigue and weakness, frequent falling, swelling of the feet and legs, and muscular and joint pain.

Early symptoms in patients with myositis include:

  • Difficulty standing up from a seated position
  • Difficulty climbing stairs
  • Difficulty lifting the arms
  • Fatigue after standing or walking a long time
  • Trouble swallowing or breathing
  • Muscle pain that does not subside within a few weeks
  • A red or purple colored rash on the eyelids, elbows, knees and knuckles

Causes and Risk Factors

Juvenile myositis generally affects children from 5 to 15 years old.

Dermatomyositis can affect all ethnic groups and both genders; however, women have been shown to be twice as likely to develop the disease.

The risk of developing polymyositis increases with age and shows the highest rates of incidence between the ages of 35 to 44 and 55 to 64. Women are also twice as likely as men to develop polymyositis.

The risk of developing IBM increases with age and usually appears in patients over the age of 50; however, patients may develop symptoms as early as their 30s. IBM is twice as likely to develop in men as in women.

Diagnosis of myositis often begins with a physical examination, to provide physicians with a better understanding of patients’ overall condition. An accurate diagnosis is important, as treatment plans are highly specialized.

The physician also may use a variety of other diagnostic tools, including blood tests, muscle biopsy, magnetic resonance imaging (MRI), electromyography (EMG) or lumbar puncture (spinal tap).


The symptoms and severity of myositis can vary greatly between individuals; an individual treatment plan developed by a knowledgeable medical team  is recommended.

Treatments may include both nondrug and drug-based therapies, including medications such as immunosuppressants or corticosteroids, which slow the body’s immune system and reduce the body’s attack on its muscles, skin and organs.

Physical therapy also may be included as a treatment to help improve the patient's physical activity and quality of life.

© 2000-2022 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.
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