Dermatomyositis (DM) is a systemic disease characterized by violaceous (heliotrope) inflammatory changes of the eyelids and periorbital area; erythema of the face, neck, and upper trunk; and flat-topped violaceous papules over the knuckles. It is associated with a polymyositis, interstitial pneumonitis, myocardial involvement, and vasculitis.
Causes of Dermatomyositis
Dermatomyositis is considered one of the connective tissue diseases, like systemic sclerosis and lupus erythematosus. Why dermatomyositis occurs remains unknown but research is taking place to identify factors that may play a part in its development, some of which are listed below.
- Genetic predisposition
- Infectious or toxic agents acting as triggers
- Underlying cancer (more likely in the elderly)
- Drug-induced
Symptoms of Dermatomyositis
The most common signs and symptoms of dermatomyositis include:
- Butterfly rash
- Skin redness or inflammation
- Red, dusky skin rash
- The rash may also affect cheeks, nose, shoulders, upper chest and elbows
- A scaly scalp and thinned out hair may occur
Diagnosis
Proximal muscle weakness with two of three laboratory criteria, i.e., elevated serum “muscle enzyme” levels, characteristic electromyographic changes, diagnostic muscle biopsy.
Treatment
Prednisone .5 to 1 mg/kg of body weight per day, increasing to 1.5 mg/kg if lower dose ineffective. Taper when “muscle enzyme” levels approach normal. Best if combined with azathioprine, 2 to 3 mg/kg/d.
Note: Steroid myopathy may occur after 4 to 6 weeks of therapy.
Alternatives Methotrexate, cyclophosphamide are alternatives, and high-dose IV immunoglobulin bolus therapy at monthly intervals spares glucocorticoid doses to achieve or maintain remissions.
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