Myositis is a group of rare diseases that causes inflammation of the muscles and persistent muscle weaknesses. In these diseases, inflammatory cells surround, invade and destroy normal muscle fibers as if they were defective or foreign to the body. In rare cases, inflammation of the heart, lungs, intestines and skin can occur.
Types of myositis include polymyositis, in which many muscles become inflamed, and dermatomyositis, in which the muscles and skin become inflamed.
All forms of myositis involve chronic muscle inflammation. This almost always results in muscle weakness, frequent falling, swollen feet and legs and muscular and joint pain. Early signs of the condition include:
- Difficulty getting up from a chair
- Difficulty climbing stairs
- Difficulty lifting the arms
- Fatigue after standing or walking a long time
- Trouble swallowing or breathing
Causes and Risk Factors
The cause of myositis is unknown. These diseases can affect people of any age. Most children who get the disease are between five and 15 years old, and most adults are 30 to 60 years old. Women are more likely to get the myositis than men.
To confirm the presence of myositis, a doctor may perform:
- A physical exam
- Blood tests
- A spinal tap
- Magnetic resonance imaging (MRI)
- Electromyography (EMG)
- A muscle biopsy
Even with the same diagnosis, two people may receive different treatments. Treatment is based on the severity and type of problems the person is experiencing. Some patients will have severe symptoms followed by periods of no symptoms at all.
Treatment may include corticosteroid drugs (usually prednisone) or drugs that suppress the immune system.