Myositis is a rare disease in which the immune system chronically inflames the body's own healthy muscle tissue. Over time, this persistent inflammation weakens muscles, often resulting in muscle aches, pain, and fatigue.
There are several types of myositis. It usually develops slowly over time with symptoms that range in severity from mild to debilitating. It can affect both children and adults.
It is not known what triggers the immune system's attack. There is no cure for myositis, however, prompt treatment for some types of myositis may prevent the disease from worsening.
- Muscle weakness. Weakness and pain in the muscles of the hips and shoulders is often a first sign of myositis. You may have difficulty getting up from a chair, combing your hair, or climbing stairs. You may become too tired to walk or stand.
- Difficulty swallowing or breathing. Myositis can affect the muscles in the front of the neck and throat, making it hard to speak or swallow (dysphagia). When it affects the lungs or chest muscles, you may have trouble breathing.
- Skin changes. People with a certain form of myositis may also develop a rash on the face, knuckles and other parts of the body.
- Other. Other possible symptoms include fever and joint pain and swelling.
Polymyositis inflames and weakens muscles in many parts of the body, especially those closest to the trunk (proximal). Dysphagia is common, as is fatigue and pain in the joints and muscles.
Dermatomyositis inflammation damages both muscle fibers and skin. Like polymyositis, you develop muscle weakness, pain and fatigue. In addition, you have a distinctive patchy, reddish rash on the eyelids, cheeks, bridge of the nose, back or upper chest, elbows, knees and knuckles. In some cases, you may develop hardened bumps under the skin.
Symptoms of inclusion-body myositis typically begin after age 50 with very gradual weakening of muscles throughout the body. You may develop dysphagia, weak wrists or fingers, and atrophy of the forearms and/or thigh muscles. Unlike other forms of myositis, inclusion-body myositis occurs more often in men than in women. There are currently no effective treatments known for inclusion-body myositis.
The most common form of myositis that affects children is dermatomyositis, with symptoms of muscle weakness, skin rash, and dysphagia.
Less commonly, children may develop juvenile forms of polymyositis and inclusion-body myositis.
Myositis can be challenging to diagnose. Symptoms vary by person and your doctor must rule out other conditions that affect muscles, such as hypothyroidism, toxin exposure, drug reactions, and genetic disorders.
Be sure to give your doctor your complete medical history, and fully describe your symptoms and when they began.
- Laboratory tests. Your physical examination will probably include one or more blood tests to look for autoantibodies and muscle enzymes such as creatine kinase (CK).
- Electromyogram. You may also need other specialized tests, such as an electromyogram (EMG), which measures the electrical activity of the muscles.
- Biopsy. Your doctor may request a muscle biopsy, in which a small piece of muscle is removed and examined under a microscope to show whether/how muscle fibers are damaged.
- Imaging. In some cases, doctors use magnetic resonance imaging (MRI) to identify areas where muscle is inflamed.
Although there is no cure for myositis, prompt and aggressive treatment to reduce inflammation of polymyositis and dermatomyositis can help prevent muscle weakness from progressing and might help restore some of your strength.
- Medications. Corticosteroids, such as prednisone, and other drugs that suppress the immune system (immunosuppresants) may slow down the attack on healthy tissue and improve skin rash. Your doctor will probably repeat blood tests throughout your treatment for myositis to monitor improvement. You may also want to use nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin or ibuprofin for pain relief.
- Exercise. After drug treatment takes effect, a program of regular stretching exercises prescribed by your doctor can help maintain range of motion in weakened arms and legs. Physical therapy may also help prevent permanent muscle shortening. Engaging in physical activity that matches your ability can help improve your mobility and quality of life. Talk to your doctor or physical therapist about an exercise program that will help you to continue your daily activities.
- Rest. Getting enough rest is an important component of managing myositis. Symptoms may worsen when you are fatigued. Try to get a full night's sleep and take short breaks during the day when you need to. You may also want to add whirlpool baths, heat, and gentle massage to your relaxation regimen.
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