When the inflammatory muscle disease polymyositis affects the skin, it is called dermatomyositis. In this condition, the eyes can be surrounded by a violet discoloration with swelling. There may be scaly, red skin over the knuckles, elbows, and knees. In addition, a red rash can occur on the face, neck, and upper chest. Hard lumps of calcium deposits can develop in the fatty layer of the skin.
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What causes dermatomyositis?
In people with polymyositis and dermatomyositis, the body’s immune system stops working well and begins attacking healthy tissues. Factors triggering this process are not known.
What are the symptoms of dermatomyositis?
Symptoms of dermatomyositis can vary a great deal from patient to patient. Some people may have the disease for months or years before seeing it. Muscle weakness may arise at the same time as the rash, or it may occur weeks, months, or years later. Some other common symptoms include:
- Reddish or bluish-purple patches, mostly on areas exposed to the sun.
- Purple spots on bony prominences, especially the knuckles.
- Discoloration with swelling around the eyes.
- Ragged cuticles and prominent blood vessels on nail folds.
- A red rash on the face, neck, shoulders, upper chest and elbows.
How is dermatomyositis diagnosed?
The diagnosis of dermatomyositis is usually confirmed by the following tests:
- Blood tests to detect increased amounts of muscle enzymes such as creatine kinase (CK) and sometimes lactic dehydrogenase (LDH).
- Blood tests to detect autoantibodies (antibodies that react with cells, tissues, or native proteins of the individual in which the antibodies are produced).
- Skin biopsy of the rash.
- Biopsy of an affected muscle.
- Electromyography (EMG) testing.
- Magnetic resonance imaging (MRI) scan of muscles.
How is dermatomyositis treated?
Doctors usually begin treatment of dermatomyositis with steroid drugs such as prednisone. Immunosuppressants may be helpful for patients who are not helped by prednisone. These include:
- Methotrexate
- Azathioprine
- Cyclophosphamide
- Chlorambucil
- Cyclosporine
- Tacrolimus
- Mycophenolate
- Rituximab
Further treatment with intravenous immunoglobulin (IVIG), used to slow down the autoimmune process, has been shown to be effective and safe. Physical therapy can preserve muscle function and prevent muscle wasting.
