Myositis refers to any condition causing inflammation in muscles. Weakness, swelling, and pain are the most common myositis symptoms. Myositis causes include infection, injury, autoimmune conditions, and drug side effects.

Types of myositis

The five types of myositis are:

  1. dermatomyositis
  2. inclusion-body myositis
  3. juvenile myositis
  4. polymyositis
  5. toxic myositis


Myositis is thought to be an autoimmune condition that causes the body to attack the muscles. Most cases don’t have a known cause. However, it’s thought that injury and infection may play a role.

Some researchers believe that myositis may also be caused by:

  • autoimmune diseases such as rheumatoid arthritis and lupus
  • viruses such as the common cold, flu, and HIV
  • drug toxicity


The symptoms of myositis vary between different people.

They can include:

  • weak and tired muscles that can make everyday tasks such as climbing stairs, brushing hair, and getting in and out of cars difficult
  • pain in muscles
  • muscles feeling tender to touch
  • muscles can sometimes swell
  • generally feeling unwell
  • weight loss
  • night sweats.
  • The most common muscles to be affected are around the shoulders, hips and thighs.
  • The weakening and tiredness in the muscles can make people with myositis more likely to fall over.
  • With dermatomyositis you can have the above symptoms as well as:
  • a red or pink rash on the upper eyelids, face and neck, and on the backs of the hands and fingers
  • swelling of the affected skin
  • puffiness and coloring around the eyes.


A doctor may suspect myositis based on a person’s symptoms of muscle weakness or other evidence of myositis. Tests for myositis include:

Blood tests: High levels of muscle enzymes, such as creatine kinase, may mean there is muscle inflammation. Other blood tests check for abnormal antibodies that may identify an autoimmune condition.

MRI scan: A scanner using a high-powered magnet and a computer creates images of the muscles. An MRI scan can help identify areas of myositis and changes in the muscles over time.

EMG: By inserting needle electrodes into muscles, a doctor can test the response of muscles to electrical nerve signals. EMG can identify muscles that are weak or damaged by myositis.

Muscle biopsy: This is the most accurate test for diagnosing myositis. A doctor identifies a weak muscle, makes a small incision, and removes a small sample of muscle tissue for testing. Muscle biopsy leads to a final diagnosis in most people with myositis.

This condition will be rated on limitation of motion of affected body part.

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