Dermatomyositis is a rare connective tissue disease characterized by inflammation of the muscles and skin. As dermatomyositis progresses, muscle tissue is wasted and gradually replaced by scar tissue. Muscle weakness is the primary symptom.
Typically affected are the large skeletal muscles (those in the arms, shoulders, pelvis, and thighs), but the heart and the involuntary muscles that control swallowing and breathing may also be involved. Some people develop polymyositis alone, which means that only muscles are affected; in others, the skin (dermis) is involved too, hence the name dermatomyositis.
Onset of symptoms may be sudden or gradual. Dermatomyositis is potentially life-threatening when vital organs are affected, but the survival rate has improved in recent years (currently about 75 percent of patients survive beyond six or seven years of diagnosis), and the majority of patients improve with treatment. Two-thirds of those afflicted with dermatomyositis are women.
What Causes Dermatomyositis?
- Although the cause of dermatomyositis is unknown, it is suspected that a virus or certain drugs might trigger the abnormal immune response.
- Dermatomyositis or polymyositis can occur alone (idiopathic) or may be associated with another rheumatic disease, such as systemic lupus erythematosus or Sjögren’s syndrome.
Symptoms of Dermatomyositis
- Weakness and stiffness are the most common symptoms. Muscle pain is less frequent; when muscle pain does occur, it commonly involves pain in the muscles of the shoulder and hip. The pain may make it difficult to perform such simple actions as brushing hair or getting out of a chair.
- Red, sometimes itchy rash on the face, neck, upper torso, and upper arms and legs. A rash may form on the knees, knuckles, elbows, or other joints or bony prominences.
- Purple discoloration and swelling of the eyelids, especially apparent upon awakening
- Skin that feels thicker than normal (over affected areas)
- Hands and feet unusually sensitive to cold (Raynaud’s phenomenon)
- Difficulty speaking or swallowing
- Weight loss
- Hardened lumps or calcinosis (sheets of calcium deposits) under the skin
- Changes in voice (dysphonia), especially hoarseness
- Dermatomyositis cannot be prevented.
Diagnosis of Dermatomyositis
- Physical examination and patient history are performed.
- Blood tests are taken to look for enzymatic evidence of muscle inflammation.
- Electromyography (which measures electrical activity in the muscles) may be performed.
- A muscle and skin biopsy may be performed to examine affected tissue under a microscope.
- Magnetic resonance imaging (MRI) scans RI) may also be performed to reveal inflammation in muscles.
- Electromyograms (EMG) may be performed to detect changes in muscles’ electrical patterns and determine which muscles are affected.
How Dermatomyositis Is Treated
- Corticosteroid drugs such as prednisone are usually prescribed (often in high doses) to reduce inflammation.
- Immunosuppressant drugs may be used if corticosteroids are not effective in relieving inflammation.
- Physical therapy may be advised to minimize shrinkage of the muscles.
- Diltiazem, a calcium channel blocker used to treat high blood pressure, and colchicine may reduce calcinosis.
- The photosensitive rash may be treated with hydroxychloroquine.
- To minimize the effects of the sun on photosensitive skin, avoid excessive sun exposure and use sun protection measures such as sunscreen.
- Severe muscle inflammation may be treated with bedrest.
- Difficulty swallowing may be treated by avoiding eating before bedtime and by raising the head of the bed.
When to Call a Doctor
- Call a doctor if you develop symptoms of dermatomyositis.
Johns Hopkins Symptoms and Remedies: The Complete Home Medical Reference
Simeon Margolis, M.D., Ph.D., Medical Editor
Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50
Updated by Remedy Health Media