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Dermatomyositis (dur-muh-to-mi-uh-SI-tis) is an uncommon disease marked by muscle weakness and a distinctive skin rash. Because of similarities in signs, symptoms and treatment, dermatomyositis is often discussed in conjunction with polymyositis.

Both conditions fall into the category of inflammatory muscle diseases — "myo" means "muscles" in Greek; "itis" means "inflamed." "Derma," which means "skin," implies the skin-related signs and symptoms that accompany the muscle inflammation of dermatomyositis.

Although dermatomyositis may occur at any age, it mostly affects adults in their late 40s to early 60s or children between 5 and 15 years of age. Women have dermatomyositis more often than men do. Dermatomyositis in children is distinct from the adult form. The disease usually develops over weeks or months.

Periods of remission, during which signs and symptoms of dermatomyositis improve spontaneously, may occur. Treatment can improve your skin and your muscle strength and function.

The most common signs and symptoms of dermatomyositis include:

• A violet-colored or dusky red rash, most commonly on your face, eyelids, and areas around your nails, knuckles, elbows, knees, chest and back. Affected areas are typically more sensitive to sun exposure.
• Progressive muscle weakness, particularly in the muscles closest to the trunk, such as those in your hips, thighs, shoulders, upper arms and neck. This weakness is symmetrical, affecting both the left and right sides of your body.
• Difficulty swallowing (dysphagia).
• Muscle pain or tenderness.
• Fatigue, fever and weight loss.
• Hardened deposits of calcium under the skin (calcinosis), especially in children.
• Gastrointestinal ulcers and infections, also more common in children.
• Lung problems.

The skin rash usually occurs at the same time as muscle weakness, but may precede muscle weakness by a few weeks. Sometimes, the skin rash alone determines the diagnosis. In some children with dermatomyositis, the skin may become thick and hard in a way similar to scleroderma. When this happens, the condition is called sclerodermatomyositis.

Weakness in muscles, such as your hips and shoulders, can lead to difficulty in getting out of chairs, climbing stairs, brushing your hair or working with your arms over your head. Weakness in your neck muscles can make it hard to hold your head up.

Dermatomyositis belongs to a group of conditions called inflammatory myopathies. Myopathies are diseases or abnormal conditions of the striated muscles that cover your skeleton. The cause of most inflammatory myopathies is unknown. Other inflammatory muscle diseases include inclusion body myositis, which progresses more slowly than other forms; myositis associated with other connective tissue diseases, such as lupus or scleroderma; and myositis associated with cancer (malignancy).

Doctors suspect that inflammatory myopathies are autoimmune disorders, in which your immune system turns against normal body components. Infections caused by bacteria, parasites or viruses can cause inflammatory myopathies, but in most cases, doctors aren't able to identify a preceding infection in dermatomyositis. Some doctors think certain people may have a genetic susceptibility to the disease.

Typically, your immune system works to protect your healthy cells from attacks by foreign substances, such as bacteria and viruses. If you have dermatomyositis, an unknown cause seems to trigger your immune system to begin producing autoimmune antibodies (also called autoantibodies) that attack your body's own tissues. Small blood vessels in muscular tissue appear to be particularly affected. Destruction of these blood vessels eventually leads to degeneration of muscle fibers. Many people with dermatomyositis show a detectable level of autoantibodies in their blood. It's unclear whether these autoantibodies are involved in causing dermatomyositis.

If you experience any of the signs or symptoms of dermatomyositis, see your doctor. The earlier the disease is detected, the better your response may be to treatment. With treatment, you can manage and sometimes even reverse your signs and symptoms.

If you have difficulty swallowing or shortness of breath, call your doctor right away, as this may indicate rapid progression of the disease and the need for immediate help.

Dermatomyositis is the most easily recognized of the inflammatory muscle diseases because of its characteristic rash. Occasionally, a rash alone may prompt a diagnosis of dermatomyositis without muscle involvement (amyopathic dermatomyositis).

In addition to a thorough evaluation, including examination of muscle strength and a detailed family medical history, your doctor may use some or all of the following tests to assist in the diagnosis:

• Electromyography. A doctor with specialized training inserts a thin needle electrode through the skin into the muscle to be tested. Electrical activity is measured as you relax or tighten the muscle. Changes in the pattern of electrical activity can confirm a muscle disease. The doctor can determine the distribution of the disease by testing different muscles.
• Blood analysis. A blood test will let your doctor know if you have elevated levels of muscle enzymes, such as creatine kinase (CK) and aldolase. Increased CK and aldolase levels can indicate muscle damage. A blood test can also determine whether autoantibodies are present in your blood.
• Muscle biopsy. A small piece of muscle tissue is removed surgically for laboratory analysis. A muscle biopsy may reveal abnormalities in your muscles, such as inflammation, damage or infection. The tissue sample can also be examined for the presence of abnormal proteins and checked for enzyme deficiencies.
• Magnetic resonance imaging (MRI). A scanner creates cross-sectional images of your muscles from data generated by a powerful magnetic field and radio waves. These images can be viewed from any direction or plane. During the test, you lie inside the cylindrical-shaped scanner for 15 minutes to an hour. MRI scans may help detect inflammation in your muscles.

If the muscles in your esophagus are affected, you may have problems swallowing (dysphagia), which in turn may cause weight loss and malnutrition. Dysphagia may also lead to entrance of food or liquids, including saliva, into your lungs (aspiration), which can lead to pneumonia. If your chest muscles are involved, you may experience breathing problems, such as shortness of breath. Gastrointestinal ulceration and bleeding can occur. Deposits of calcium in your muscles, skin and connective tissues (calcinosis) can occur late in the disease, particularly if you've had the disease for a long time.

Dermatomyositis may be associated with other conditions, including:

• Raynaud's phenomenon. This is a condition in which your fingers, toes, cheeks, nose and ears turn pale when exposed to cold temperatures.
• Other connective tissue diseases. Diseases that affect tissues that hold your body together, such as your muscles and joints, sometimes occur in conjunction with each other. Conditions such as lupus, rheumatoid arthritis, scleroderma and Sjogren's syndrome can occur in combination with dermatomyositis.
• Cardiovascular disease. The muscle of your heart may become inflamed (myocarditis). In a small number of people who have dermatomyositis, congestive heart failure and heart arrhythmias may develop.
• Lung disease. A condition called interstitial lung disease may occur with dermatomyositis. Interstitial lung disease refers to a group of disorders that cause scarring (fibrosis) of lung tissue, making lungs stiff and inelastic. Signs and symptoms include a dry cough and shortness of breath.
• Cancer. Dermatomyositis in adults has been linked to an increased likelihood of cancer, particularly of the lungs, breasts, ovaries and gastrointestinal tract. Risk of cancer increases with age, although it appears to level off three years after a diagnosis of dermatomyositis.

The outcome (prognosis) of dermatomyositis tends to be better if there are no associated complications, such as esophageal damage, lung disease or cancer. Early diagnosis is important, because it can lead to prompt treatment and evaluation of associated conditions. Early treatment of children can prevent the development of calcinosis, a condition that can be hard to treat once it's established.

Pregnancy may worsen signs and symptoms in women with active disease. Active dermatomyositis can also increase the risk of premature birth or stillbirth. If the disease is in remission, the risk isn't as great.

People with polymyositis or dermatomyositis may also be at an increased risk of infections, particularly respiratory and digestive infections. As a result, your doctor may monitor your signs and symptoms for any indication of infection so that you can receive prompt diagnosis and treatment.

Although there's no cure for dermatomyositis, treatment can improve your skin, muscle strength and function. Treatment begun early in the disease process tends to be more effective, often because there are fewer complications. Methods of therapy include the following:

• Corticosteroids. These medications suppress your immune system, limiting the production of antibodies and reducing skin and muscle inflammation. Corticosteroids, especially prednisone, are usually the first choice in treating inflammatory myopathies such as dermatomyositis. Your doctor may start with a very high dose, and then decrease it as your signs and symptoms improve. This generally takes about two to four weeks. Your doctor may also prescribe topical corticosteroids for your skin. Visible results are usually evident within three to six months, but therapy is often needed for years. Prolonged use of corticosteroids can have serious side effects including osteoporosis, weight gain, diabetes, increased risk of someinfections, mood swings, cataracts, high blood pressure, a redistribution of body fat and muscle weakness. As a result, your doctor may also recommend supplements such as calcium and vitamin D and may prescribe bisphosphonates such as alendronate (Fosamax) or risedronate (Actonel).
• Immunosuppressants. If your body doesn't respond adequately to corticosteroids, your doctor may recommend other immunosuppressive drugs such as azathioprine (Imuran) or methotrexate (Rheumatrex). Your doctor may prescribe these alone or in combination with corticosteroids. When in combination, these additional immunosuppressants can be used to lessen the dose and potential side effects of the corticosteroid. Immunosuppressants such as cyclophosphamide (Cytoxan) and cyclosporine (Neoral, Sandimmune) may improve signs and symptoms of dermatomyositis and interstitial lung disease.
• Antimalarial medications. For a persistent rash, your doctor may prescribe an antimalarial medication such as hydroxychloroquine (Plaquenil) or chloroquine phosphate (Aralen). Be aware, however, that adverse reactions to such medications, though uncommon, can be confused with the rash or weakness of dermatomyositis itself.
• Intravenous immunoglobulin (IVIg). This involves receiving intravenous infusions of antibodies from a group of donors over two to five days. This treatment is still under investigation and is usually expensive. It may be an option for you if your dermatomyositis is severe or resistant to other forms of therapy.
• Physical therapy. A physical therapist can show you various exercises to maintain and improve your strength and flexibility and advise an appropriate level of activity. Your exercise program is likely to change during the course of the disease and treatment period. Keeping active in general and pacing yourself will help maintain muscle strength.
• Surgery. Surgery may be an option to remove painful calcium deposits.
• Pain relievers. Over-the-counter drugs such as aspirin, ibuprofen (Advil, Motrin, others) and acetaminophen (Tylenol, others), can be used to treat any accompanying pain. If these aren't sufficient, your doctor may prescribe a stronger pain reliever, such as codeine.

Treatments with unknown long-term effects include:

• Plasmapheresis. This treatment, also called plasma exchange, is a type of blood cleansing in which damaging antibodies are removed from your blood.
• Radiation therapy. This involves irradiation of the lymph nodes to suppress your immune system.

Treatments that are still in the experimental phase but have shown signs of being effective include fludarabine (Fludara), an agent that prevents the development and growth of malignant cells, and tacrolimus (Prograf), a transplant-rejection drug that may work to inhibit the immune system. Tacrolimus is often used topically to treat dermatomyositis and other skin problems.

Living with a chronic autoimmune disease can make you wonder at times whether you're up to the challenge. Though it isn't always easy, you're tougher than you may think. To help you cope, try supplementing your medical care with the following suggestions:

• Know your illness. Read all you can about dermatomyositis and other muscle and autoimmune disorders. Talk to other people who have a similar condition. Don't be afraid to ask your doctor any questions that you may have concerning your illness, diagnosis or treatment plan.
• Be a part of your medical team. Consider yourself, your doctor and any other medical experts involved as a united front in the fight against your disease. Following the treatment plan you agreed to is vital. Keep your doctor updated on any new signs or symptoms you may experience. Regularly perform the physical exercises prescribed for you. A speech therapist can help you with swallowing difficulties and a registered dietitian can help you with preparing easy-to-eat foods.
• Treat yourself well. Don't wait until you're exhausted to rest. This will only set you back further as your body tries to recuperate. Learning to pace yourself can help you maintain a consistent level of energy, accomplish just as much and feel better emotionally. Learn to say no effectively and ask for help when you need it. Take hot baths, stretch, exercise.
• Wear sunscreen. Areas affected by your rash are more sensitive to the sun, so wear protective clothing or high-protection sunscreen when you go out.
• Use electric appliances, power tools and other aids. Save your energy using power appliances, such as battery-operated toothbrushes, electric can openers and power screwdrivers. If your ability to walk is impaired, consider using an aid such as a cane, walker or wheelchair.
• Accept your emotions. Denial, anger and frustration are normal feelings when you must deal with an illness. Things don't seem normal or fair and likely seem out of your control. Feelings of fear and isolation are common, so stay close to your family and friends. Try to maintain your daily routine as best you can and don't neglect doing those things you enjoy. Many people find support groups to be a helpful resource.