Diseases & Conditions

Dermatomyositis

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.

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.