Dermatomyositis is an acquired muscle disease. It is classified as an inflammatory myopathy. The disease, which has a gradual beginning, affects both children and adults. Females are more often affected than males.
The most common symptom is muscle weakness, usually affecting those muscles that are closest to the trunk of the body. Eventually, patients have problems rising from a sitting position, climbing stairs, lifting objects, or reaching overhead. The muscle weakness is usually accompanied by pain and swelling.
A rash is often seen before the muscle weakness occurs. The rash is bluish-purple patches on the face, neck, shoulders, upper chest, elbows, knees, knuckles, and back. There may be swelling of the face and eyelids. The rash may be itchy.
Hardened bumps of calcium deposits may develop under the skin, especially in children. Trouble with swallowing, talking, and breathing may occur.
Occasionally, the muscles ache and are tender to touch.
Patients may also feel fatigue and discomfort and have weight loss or a low-grade fever.
In some cases, muscles not close to the trunk may be affected later in the course of the disease.
One treatment is a steroid called prednisone. For patients in whom prednisone is not effective, other drugs that suppress the immune system may be prescribed. Recently, the part of the blood that fights disease (immunoglobulin) was shown to be effective in treatment. Physical therapy is usually advised to preserve muscles and avoid the thinning of muscles (atrophy).
Most cases respond to therapy. The disease is usually more severe and resistant to therapy in patients with heart or lung problems.