Myositis (my-OH-sigh-tiss) is a rare disease in which the immune system chronically inflames the body's own healthy muscle tissue. Persistent inflammation progressively weakens the muscles.
No one knows what triggers the immune system's attack. Myositis can take several forms, usually develops slowly over time and can range in severity from mild to debilitating or worse. Both children and adults can get it.
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.
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.
People with a certain form of myositis may also develop a rash on the face, knuckles and other parts of the body. Other possible symptoms include fever and joint pain and swelling. See your doctor right away for diagnosis and treatment.
Myositis can be challenging to diagnose. Symptoms vary by person and your doctor must rule out other conditions that affect muscles (i.e., hypothyroidism, toxin exposure, drug reactions, and genetic disorders).
Give your doctor your complete medical history, and describe your symptoms and when they began.
Your physical examination will probably include one or more blood tests to look for autoantibodies and muscle enzymes such as creatine kinase (CK). You may also need other specialized tests, such as an electromyogram (EMG), which measures the electrical pattern of the muscles.
Your doctor may request a muscle biopsy, in which a small piece of muscle is removed, stained and examined by microscope to show whether/how fibers are damaged.
Sometimes your doctor may use magnetic resonance imaging (MRI) to identify areas where muscle is inflamed.
Forms of Myositis
PM 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.
DM inflammation damages both muscle fibers and skin. Like PM, 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.
Inclusion Body Myositis (IBM)
Symptoms of IBM 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, IBM occurs more often in men than in women and, unfortunately, there are no effective treatments known for IBM.
Juvenile Myositis (JM)
Although some children develop juvenile forms of PM and IBM, children usually get juvenile DM with symptoms of muscle weakness, skin rash and dysphagia.
Although there is no cure for myositis, prompt and aggressive treatment to reduce inflammation of PM and DM can help prevent muscle weakness from progressing and might help restore some of your strength.
- Medications: Corticosteroids (i.e., 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. You may also want to add whirlpool baths, heat and gentle massage.
- Rest: Getting enough rest is an important component of managing myositis. Take frequent breaks during the day and limit your activity.
The American Academy of Orthopaedic Surgeons
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