Dermatomyositis is a rare disease that causes muscle inflammation and skin rash. It's one of a group of muscle diseases that cause muscle inflammation, weakness, and swelling. It's different from other muscle diseases because it also causes inflammatory skin rashes. Dermatomyositis is the term used to describe both muscle and skin symptoms, but some people will have only one or the other.

It can occur at any age, but it most often affects adults ages 50 to 70. People who are biologically female are twice as likely to be diagnosed with the disease. Some people with the disease also have a connective tissue disorder, such as lupus or rheumatoid arthritis.

The exact cause is not known. But dermatomyositis can be linked to cancer, other autoimmune diseases, infections, or genetic problems.

Swelling and inflammation in the blood vessels that supply your skin and muscles cause symptoms, such as:

• Red or purple rash on sun-exposed areas that may be painful or itchy.
• Red or purple swelling of the upper eyelids.
• Red or purple spots on the knuckles, elbows, knees, and toes (Gottron papules).
• Joints that feel stiff and turn pale and painful in cold conditions and feel better when warmed (Raynaud's phenomenon).
• Scaly, rough, dry skin, which can lead to hair thinning.
• Swollen or red or purple area around the fingernails.
• Hard lumps under the skin caused by calcium deposits (calcinosis).
• Muscle weakness in the neck, hip, back, and shoulders.
• Muscle aches.
• Trouble swallowing and voice changes.
• Tiredness, fever, and weight loss.
• Trouble getting up from a chair or getting out of bed due to muscle weakness.

Sometimes the muscle inflammation can spread to other parts of the body including the heart, gastrointestinal tract, and lungs. Lung involvement can cause breathing trouble and coughing. Adults may have a low-grade fever, along with lung inflammation and sensitivity to light.

Your doctor will first review your health history and do a physical exam. They'll look for an underlying disease, such as cancer. Your doctor may also do the following tests:

• Blood tests. These are done to look for signs of muscle inflammation. They also check for abnormal proteins that form in autoimmune disease. The most common blood tests include muscle enzyme creatine kinase and the antinuclear antibody.
• Electromyogram. This may be done to find abnormal electrical activity in affected muscles.
• MRI. This test uses a magnetic field and radio waves to create detailed images of tissues.
• Skin or muscle biopsy. Tiny pieces of skin or muscle tissue are taken and looked at under a microscope.

Treatment will depend on your symptoms, age, and general health. There's no cure for the condition, but the symptoms can be managed. You may need more than one kind of treatment. And your treatment may need to be changed over time. Treatments include:

• Physical therapy. Special exercises help to stretch and strengthen the muscles. Orthotics or assistive devices may be used.
• Skin treatment. You may need to prevent sun exposure and wear sunscreen to help prevent skin rashes. Your doctor can treat itchy skin rashes with antihistamine medicines or with anti-inflammatory steroid creams.
• Anti-inflammatory medicines. These are steroid medicines, or corticosteroids. They ease inflammation in the body. They may be given by mouth or through an I.V. (intravenous) line.
• Immunosuppressive medicines. These medicines block or slow down your body's immune system.
• Immunoglobulin. If you have not responded to other treatments, your doctor may prescribe these medicines. They are donated blood products that may boost your body's immune system. They are put directly into your bloodstream through an I.V. line.
• Surgery. You may need surgery to remove the calcium deposits (calcinosis) under the skin if they become painful or infected.

Talk with your doctor about the risks, benefits, and possible side effects of all medicines.

Possible problems for some people with dermatomyositis include lung disease, heart disease, or cancer. These can make treatment more difficult.

If you have dermatomyositis, you may need treatment for the rest of your life. It's important to learn as much as you can about the disease. Work closely with your doctor. Researchers are studying causes and treatments for the condition. Early diagnosis and treatment for the disease may improve over time.

If your symptoms get worse or you notice new symptoms, contact your doctor.

• Dermatomyositis is a rare disease that causes muscle weakness and skin rash.
• Symptoms include a red or purple rash on sun-exposed skin and eyelids, calcium deposits under the skin, muscle weakness, and trouble talking or swallowing.
• There is no cure, but treatment is done to reduce the symptoms.
• Complications include lung disease, heart disease, and cancer.

Tips to help you get the most from a visit to your doctor:

• Know the reason for your visit and what you want to happen.
• Before your visit, write down questions you want answered.
• Bring someone with you to help you ask questions and remember what your doctor tells you.
• At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your doctor gives you.
• Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.
• Ask if your condition can be treated in other ways.
• Know why a test or procedure is recommended and what the results could mean.
• Know what to expect if you don't take the medicine or have the test or procedure.
• If you have a follow-up appointment, write down the date, time, and purpose for that visit.
• Know how you can contact your doctor if you have questions, especially after office hours or on weekends.