The most common signs and symptoms of dermatomyositis include:
- Skin changes. A violet-colored or dusky red rash develops, most commonly on your face and eyelids and on knuckles, elbows, knees, chest and back. The rash, which can be itchy and painful, is often the first sign of dermatomyositis.
- Muscle weakness. Progressive muscle weakness involves the muscles closest to the trunk, such as those in your hips, thighs, shoulders, upper arms and neck. The weakness affects both the left and right sides of your body, and tends to gradually worsen.
When to see a doctor
Seek medical attention if you develop muscle weakness or an unexplained rash.
The cause of dermatomyositis is unknown, but the disease has much in common with autoimmune disorders, in which your immune system mistakenly attacks your body tissues.
Small blood vessels in muscular tissue are particularly affected in dermatomyositis. Inflammatory cells surround the blood vessels and eventually lead to destruction of muscle fibers.
Possible complications of dermatomyositis include:
- Difficulty swallowing. If the muscles in your esophagus are affected, you can have problems swallowing (dysphagia), which can cause weight loss and malnutrition.
- Aspiration pneumonia. Difficulty swallowing can also cause you to breathe food or liquids, including saliva, into your lungs (aspiration).
- Breathing problems. If the condition affects your chest muscles, you might have breathing problems, such as shortness of breath.
- Calcium deposits. These can occur in your muscles, skin and connective tissues (calcinosis) as the disease progresses. These deposits are more common in children with dermatomyositis and develop earlier in the course of the disease.
Dermatomyositis may cause other conditions or put you at higher risk of developing them, including:
- Raynaud's phenomenon. This condition causes your fingers, toes, cheeks, nose and ears to 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 with dermatomyositis (overlap syndromes).
- Cardiovascular disease. Dermatomyositis can cause heart muscle inflammation (myocarditis). In a small number of people who have dermatomyositis, congestive heart failure and heart arrhythmias develop.
- Lung disease. Interstitial lung disease can occur with dermatomyositis. Interstitial lung disease refers to a group of disorders that cause scarring (fibrosis) of lung tissue, making the 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 developing 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. Dermatomyositis can also develop after you receive a diagnosis of cancer.