Myositis is chronic muscle inflammation, muscle weakness and pain. Two common types of myositis are polymyositis and dermatomyositis.

Polymyositis (PM)

PM is an inflammatory muscle disease that involves not only the skeletal muscles but also the blood vessels that carry blood to the muscles. It is more common in women older than 20, onset is usually between ages 30 and 60.

Symptoms include:
Progressive muscle weakness that typically affects the muscles of the hips and thighs and the upper arms, back, shoulders and neck. Weakness is accompanied by pain and tenderness, and fatigue. Weakness and fatigue can lead to tripping or falling, difficulty swallowing, speaking, lifting, and reaching. Complications can include arthritis, shortness of breath, heart arrhythmias, and congestive heart failure. Fine motor skills like writing, typing, playing piano are only affected later in the disease process.

Dermatomyositis (DM)

Dermatomyositis is an inflammatory disease of the muscles accompanied by muscle weakness and a skin rash that precedes or accompanies progressive muscle weakness. The rash is patchy with purple or red discolorations that typically develops on the eyelids and on the muscles that straighten the joints such as the knuckles, elbows, knees, and toes. However, the rash can extend to the face, neck, shoulders, upper chest, back and other locations.

Other symptoms include weight loss, a low-grade fever, joint pain, light sensitivity, lung inflammation, and calcium deposits under the skin or in the muscles. In some cases, the heart and gastrointestinal system can be involved. 10-20% of DM patients also have malignancy. This type of myositis can affect children as well as adults. Onset can occur at any age, but adults typically have onset around age 50; and ages 5-10 in children.

What is the cause of myositis?

Myositis is an autoimmune disease. The cause is unclear but viral infections have been implicated.

Who is at risk?

Both adults and children but dermatomyositis is the common chronic form in children. Both forms of myositis are twice as common in women as in men.

How is myositis diagnosed?

Your Ortho Illinois doctor will review your medical history, conduct a physical examination including testing muscle strength, and order blood tests. An EMG (electromyography will measure electrical activity generated by the muscles. An ultrasound will be ordered to evaluate inflammation and an MRI may be ordered to evaluate muscle anatomy. Other tests may be needed. The results of the exam and tests will establish the diagnosis.

What is the treatment for myositis?

There is no cure, but symptoms can be treated with medication, physical therapy, heat therapy, orthotics, assistive devices and rest. Oral or IV steroids are standard treatment. Immunosuppressive drugs and IV immunoglobulin can improve symptoms. Physical therapy can prevent muscle atrophy and topical steroids can treat the rash.

The symptoms of dermatomyositis usually resolve with therapy. However, polymyositis patients may have more severe disease and disability.

The rheumatology team at Ortho Illinois have the experience and expertise to diagnose and treat myositis.