Dermatomyositis (dur-muh-to-mi-uh-SI-tis) is an uncommon inflammatory disease marked by muscle weakness and a distinctive skin rash.

Dermatomyositis may occur at any age, but it mostly affects adults in their late 40s to early 60s, or children between 5 and 15 years of age. Dermatomyositis affects more women than men. The signs and symptoms of dermatomyositis usually develop gradually, over weeks or months.

Periods of remission, when symptoms of dermatomyositis improve spontaneously, may occur. Treatment can clear the skin rash and help you regain 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. The rash, which can be patchy with bluish-purple discolorations, is often the first sign of dermatomyositis.
• Progressive muscle weakness, particularly in the muscles closest to the trunk, such as those in your hips, thighs, shoulders, upper arms and neck. The weakness is symmetrical, affecting both the left and right sides of your body, and tends to gradually worsen.

Other dermatomyositis signs and symptoms that may occur include:

• 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 intestinal perforations, also more common in children
• Lung problems

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Your immune system

Dermatomyositis is in a group of diseases or disorders of the muscles called inflammatory myopathies. The cause of most inflammatory myopathies is unknown.

Infections caused by bacteria, parasites or viruses can cause inflammatory myopathies, but in most cases of dermatomyositis, doctors aren't able to identify a preceding infection. Some doctors think certain people may have a genetic susceptibility to the disease.

Inflammatory myopathies share many characteristics with autoimmune disorders, in which your immune system attacks normal body components. Normally, 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 may act as a trigger for your immune system to begin producing autoimmune antibodies (autoantibodies) that attack your body's own tissues.

Small blood vessels in muscular tissue are particularly affected in dermatomyositis. Inflammatory cells surround the blood vessels and eventually lead to degeneration of muscle fibers. Many people with dermatomyositis show a detectable level of autoantibodies in their blood.

Possible complications of dermatomyositis include:

Muscle weakness complications

• Difficulty swallowing. If the muscles in your esophagus are affected, you may have problems swallowing (dysphagia), which in turn may cause weight loss and malnutrition.
• Aspiration and pneumonia. Difficulty swallowing may also lead to entrance of food or liquids, including saliva, into your lungs (aspiration), which can lead to pneumonia.
• Breathing problems. If your chest muscles are affected by the disease, you may experience breathing problems, such as shortness of breath.
• Gastrointestinal problems. Gastrointestinal ulceration and bleeding can occur.

Skin symptom complications

• Calcium deposits. Late in the disease, deposits of calcium can occur in your muscles, skin and connective tissues (calcinosis). These deposits develop earlier and are more common in children with dermatomyositis.
• Infections. Dermatomyositis puts you at increased risk of infections, particularly of the respiratory and digestive tracts.

Associated conditions
Dermatomyositis may cause other conditions, or put you at higher risk of developing them. These conditions include:

• 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. Other conditions such as lupus, rheumatoid arthritis, scleroderma and Sjogren's syndrome can occur in combination with dermatomyositis.
• Cardiovascular disease. Dermatomyositis may cause the muscle of your heart to 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 cervix, lungs, pancreas, breasts, ovaries and gastrointestinal tract. Risk of cancer increases with age, although it appears to level off three years or so after a diagnosis of dermatomyositis. The diagnosis of cancer may also happen before you develop dermatomyositis.

Concerns during pregnancy
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.

What you can do
When you go in to see your doctor, be sure to have a record of your symptoms. Write down when and where any skin rash started, and whether it's changed color or spread to other areas. You may also want to think back to when you started feeling weaker, and which muscles have been affected.

What to expect from your doctor
Your doctor will ask you detailed questions about your symptoms and family history, as well as completing a thorough physical examination. If you have a rash, your doctor will examine it carefully. Different types of strength tests also are part of the examination. If your doctor suspects dermatomyositis, more tests will be ordered.

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 (called amyopathic dermatomyositis), even if you don't have any muscle weakness.

In addition to assessing your signs and symptoms, your doctor may use other tests to confirm a diagnosis of dermatomyositis.

Imaging tests

• Magnetic resonance imaging (MRI). A scanner creates cross-sectional images of your muscles from data generated by a powerful magnetic field and radio waves.

  As MRI has become more sensitive, doctors have been using it more to diagnose inflammatory myopathies. MRI can detect active inflammation in your muscles, fibrosis and calcification. Its high sensitivity can detect subtle muscle inflammation and swelling early in the disease. A benefit of MRI is that it can look at large amounts of muscle to look for patterns or patches of muscle weakness, instead of taking a small sample from a single muscle, for example.

Muscle tests

• 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, and 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.
• Muscle biopsy. A small piece of muscle tissue is removed surgically for laboratory analysis. In dermatomyositis, inflammatory cells surround and damage the capillary blood vessels in the muscle. A muscle biopsy may reveal inflammation in your muscles or other problems, like damage or infection. The tissue sample can also be examined for the presence of abnormal proteins and checked for enzyme deficiencies.

Blood and skin tests

• 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 detect specific autoantibodies associated with different symptoms of dermatomyositis, which can help in determining the best medication and treatment.
• Skin biopsy. A small piece of skin is removed for laboratory analysis. The skin sample can confirm the diagnosis of dermatomyositis and rule out other disorders, such as lupus. If the skin biopsy confirms the diagnosis, a muscle biopsy may not be necessary.

There's no cure for dermatomyositis, but treatment can improve your skin and your muscle strength and function. The earlier treatment is started in the course of dermatomyositis, the more effective it is, leading to fewer complications.

Drugs

• Corticosteroids. These medications suppress your immune system, limiting the production of antibodies and reducing skin and muscle inflammation, as well as improving muscle strength and function. 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. Improvement generally takes about two to four weeks, but therapy is often needed for years. Your doctor may also prescribe topical corticosteroids for your skin.

  Prolonged use of corticosteroids can have serious and wide-ranging side effects, so your doctor may recommend supplements to combat them, such as calcium and vitamin D, and may prescribe bisphosphonates, such as alendronate (Fosamax), risedronate (Actonel) or zoledronic acid (Reclast). Bisphosphonates taken in pill form may not be recommended if you have difficulty swallowing.

• Corticosteroid-sparing agents. Your doctor may recommend other medications, either to decrease side effects or if your condition doesn't respond to corticosteroids. These medications include azathioprine (Imuran) or methotrexate (Rheumatrex). Your doctor may prescribe these alone or in combination with corticosteroids.

  Immunosuppressants, such as cyclophosphamide (Cytoxan) and cyclosporine (Neoral, Sandimmune), also 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 (Aralen).
• Pain relievers. Over-the-counter drugs such as aspirin, ibuprofen (Advil, Motrin, others) and acetaminophen (Tylenol, others), can be used to treat pain. If these aren't sufficient, your doctor may prescribe a stronger pain reliever, such as codeine.

Antibody therapy

• Intravenous immunoglobulin (IVIg). Immunoglobulin contains healthy antibodies from blood donors. High doses can block the damaging antibodies that attack muscle and skin in dermatomyositis.

Immunosuppressive therapies
In addition to corticosteroids and immunosuppressive drugs, other treatments to suppress your immune system include:

• Tacrolimus (Prograf). This transplant-rejection drug may work to inhibit the immune system. Tacrolimus is often used topically to treat dermatomyositis and other skin problems. When taken orally, it may be helpful if you have dermatomyositis complicated by interstitial lung disease.

Investigational treatment

• Biological therapies. Rituximab (Rituxan), which depletes a certain type of lymphocyte (B cells), has been studied in small numbers of people with polymyositis and dermatomyositis and shown to improve muscle strength, lung involvement and skin rash. Tumor necrosis factor (TNF) inhibitors such as etanercept (Enbrel) and infliximab (Remicade) have not been shown to be effective in trials with small numbers of people with polymyositis or dermatomyositis. Rituximab is not approved by the Food and Drug Administration for the treatment of dermatomyositis, so your insurance company will likely require preapproval if you wish to be reimbursed.

Therapies

• Physical therapy. A physical therapist can show you exercises to maintain and improve your strength and flexibility and advise an appropriate level of activity.
• Speech therapy. If your swallowing muscles are weakened by dermatomyositis, speech therapy can help you learn how to compensate for those changes.
• Dietetic assessment. Later in dermatomyositis, chewing and swallowing can become more difficult. A registered dietitian can teach you how to prepare easy-to-eat foods.

Other treatments

• Surgery. Surgery may be an option to remove painful calcium deposits and prevent recurrent skin infections.

• Get active. Maintaining an exercise routine can help you maintain and build your muscle strength. Just be sure that you get a detailed plan and recommendations from your doctor or physical therapist before starting an exercise program.
• Rest when you're tired. Don't wait until you're exhausted. 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.
• 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.

Living with a chronic autoimmune disease can make you wonder at times whether you're up to the challenge. 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.
• Know and assert your limits. Learn to say no effectively and ask for help when you need it.
• Acknowledge 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.