Dermatomyositis
Dermatomyositis is a disease that involves muscle inflammation and a skin rash. Polymyositis is a similar inflammatory condition that also involves muscle weakness, swelling, tenderness, and tissue damage but no skin rash. Both are part of a larger group of diseases called myopathies, more specifically inflammatory myopathies.
Polymyositis
Polymyositis and dermatomyositis are rare inflammatory diseases. These diseases lead to muscle weakness, swelling, tenderness, and tissue damage. T...
Causes
The cause of dermatomyositis is unknown. Experts think it may be due to a viral infection of the muscles or a problem with the body's immune system. It may also occur in people who have cancer in the abdomen, lung, or other parts of the body.
Anyone can develop this condition. It most often occurs in children age 5 to 15 and adults age 40 to 60. It affects women more often than men.
Symptoms
Symptoms may include:
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Muscle weakness, stiffness, or soreness
Muscle weakness
Weakness is reduced strength in one or more muscles.
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- Purple-red skin rash
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Shortness of breath
Shortness of breath
Breathing difficulty may involve:Difficult breathing Uncomfortable breathingFeeling like you are not getting enough air
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Difficulty swallowing
Difficulty swallowing
Difficulty with swallowing is the feeling that food or liquid is stuck in the throat or at any point before the food enters the stomach. This proble...
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The muscle weakness may come on suddenly or develop slowly over weeks or months. You may have trouble raising your arms over your head, getting up from a sitting position, and climbing stairs.
The rash may appear on your face, knuckles, neck, shoulders, upper chest, and back.
Exams and Tests
The health care provider will do a physical exam. Tests may include:
- Bloods test to check levels of muscle enzymes called creatine phosphokinase and aldolase
Aldolase
Aldolase is a protein (called an enzyme) that helps break down certain sugars to produce energy. It is found in high amount in muscle and liver tiss...
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Electrocardiogram (ECG)
Electrocardiogram
An electrocardiogram (ECG) is a test that records the electrical activity of the heart.
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Electromyography (EMG)
Electromyography
Electromyography (EMG) is a test that checks the health of the muscles and the nerves that control the muscles.
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Magnetic resonance imaging (MRI)
Magnetic resonance imaging
A magnetic resonance imaging (MRI) scan is an imaging test that uses powerful magnets and radio waves to create pictures of the body. It does not us...
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Muscle biopsy
Muscle biopsy
A muscle biopsy is the removal of a small piece of muscle tissue for examination.
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Skin biopsy
Skin biopsy
A skin lesion biopsy is when a small amount of skin is removed so it can be examined under a microscope. The skin is tested to look for skin conditi...
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Chest x-ray and CT scan of the chest
Chest x-ray
A chest x-ray is an x-ray of the chest, lungs, heart, large arteries, ribs, and diaphragm.
ImageRead Article Now Book Mark ArticleCT scan of the chest
A chest CT (computed tomography) scan is an imaging method that uses x-rays to create cross-sectional pictures of the chest and upper abdomen....
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Lung function tests
Lung function tests
Pulmonary function tests are a group of tests that measure breathing and how well the lungs are functioning.
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Swallowing study
Swallowing study
Esophageal manometry is a test to measure how well the esophagus is working.
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Treatment
The initial treatment is the use of corticosteroid medicines. The dose of medicine is slowly tapered off as muscle strength improves. This takes about 4 to 6 weeks. You may stay on a low dose of a corticosteroid medicine after that.
Medicines to suppress the immune system may be used to replace the corticosteroids. These medicines may include azathioprine, methotrexate or mycophenolate.
Treatments that may be tried when disease that remains active in spite of these medicines are:
- Intravenous gamma globulin
- Biologic medicines
When your muscles get stronger, your provider may tell you to slowly cut back on your doses. Many people with this condition must take a medicine called prednisone for the rest of their lives.
If a tumor is causing the condition, the muscle weakness and rash may get better when the tumor is removed.
Outlook (Prognosis)
It is important to be followed by a health care provider when you have dermatomyositis. Severe illness can lead to disability and can sometimes result in death.
Symptoms may go away completely in some people, such as children.
The condition may be fatal in adults due to:
- Severe muscle weakness
- Malnutrition
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Pneumonia
Pneumonia
Pneumonia is inflamed or swollen lung tissue due to infection with a germ. This article covers community-acquired pneumonia (CAP). This type of pneu...
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The major causes of death with this condition are cancer and lung disease.
People with lung disease with the anti-MDA-5 antibody have a poor prognosis in spite of current treatment.
Possible Complications
Complications may include:
- Lung disease
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Acute renal failure
Acute renal failure
Acute kidney failure is the rapid (less than 2 days) loss of your kidneys' ability to remove waste and help balance fluids and electrolytes in your b...
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Malignancy
The term malignancy refers to the presence of cancerous cells that have the ability to spread to other sites in the body (metastasize) or to invade n...
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Inflammation of the heart
Inflammation of the heart
Pericarditis is a condition in which the sac-like covering around the heart (pericardium) becomes inflamed.
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When to Contact a Medical Professional
Contact your provider if you have muscle weakness or other symptoms of this condition.
Reviewed By
Diane M. Horowitz, MD, Rheumatology and Internal Medicine, Northwell Health, Great Neck, NY. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
Dinulos JGH. Connective tissue diseases. In: Dinulos JGH, ed. Habif's Clinical Dermatology. 7th ed. Philadelphia, PA: Elsevier; 2021:chap 17.
Greenberg SA. Inflammatory myopathies. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 248.
Nagaraju K, Aggarwal R, Lundberg IE. Inflammatory diseases of muscle and other myopathies. In: Firestein GS, McInnes IB, Koretzky GA, Mikuls TR, Neogi T, O'Dell JR, eds. Firestein & Kelley's Textbook of Rheumatology. 12th ed. Philadelphia, PA: Elsevier; 2025:chap 86.
National Organization for Rare Disorders website. Dermatomyositis. rarediseases.org/rare-diseases/dermatomyositis/. Updated May 4, 2018. Accessed February 27, 2025.
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