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Medically reviewed by Last updated on May 2, 2022.

What is dermatomyositis?

Dermatomyositis (DM) is a muscle disease that causes inflammation and a skin rash.

What causes DM?

The cause of DM may not be known. It may be caused by a virus. Problems with your immune system may cause this disease. DM may cause your immune system to attack your muscle tissues.

What are the signs and symptoms of DM?

  • Muscle weakness is one of the 2 most common symptoms of DM. It develops in your hips, thighs, upper arms, shoulders, and neck and slowly gets worse. You may have trouble standing up after sitting in a chair. You may also have trouble climbing stairs, lifting objects, and combing your hair.
  • A rash is the other most common sign of DM. A dark red or violet rash develops on your face and eyelids. You may also have a rash on your chest, back, elbows, knuckles, and knees. The rash will often get worse after exposure to the sun.
  • Other symptoms that may develop include trouble swallowing, muscle pain, and hard bumps under the skin.

How is DM diagnosed?

  • A biopsy may be done to collect a sample of your muscle and skin. These are sent to a lab for tests.
  • Blood tests will show the level of damage to your muscles.
  • An electromyography (EMG) is used to test the function of your muscles and the nerves that control them. Wires are placed on the area of muscle being tested. Needles that enter your skin may be attached to the electrodes. The electrical activity of your muscles and nerves is measured by a machine attached to the electrodes. Your muscles are tested at rest and with activity.
  • An MRI takes pictures of your muscles and skin to show damage. You may be given dye to help the pictures show up better. Tell the healthcare provider if you have ever had an allergic reaction to contrast dye. Do not enter the MRI room with anything metal. Metal can cause serious injury. Tell the healthcare provider if you have any metal in or on your body.

How is DM treated?

You may need medicines to decrease pain, rash, swelling, and itching. You may also need medicine to slow the attack on your muscles by your immune system.

Treatment options

The following list of medications are in some way related to or used in the treatment of this condition.

View more treatment options

How can I manage my symptoms?

  • Go to physical and occupational therapy. A physical therapist teaches you exercises to help improve movement and strength, and to decrease pain. An occupational therapist teaches you skills to help with your daily activities.
  • Massage and stretch your muscles to help prevent stiffness and loss of movement.
  • Hydrotherapy is a gentle water exercise program. It may strengthen muscles and help improve movement.

How should I protect my skin?

  • Wear sunscreen that is SPF15 or higher. It should also have UVA and UVB protection. Reapply sunscreen often if you go swimming or are sweating heavily. Protect your lips by using lipsticks and lip balms that contain sunscreen.
  • Stay out of the sun in the middle of the day. The sun is strongest and most harmful to your skin between 10am and 2pm.
  • Cover your skin. Wear long-sleeved shirts and pants when you are out in the sun. Wear a hat with a wide brim to protect both your face and neck.
  • Do not use tanning booths. These can damage your skin as much as the sun.

When should I contact my healthcare provider?

  • You have a fever.
  • You are depressed.
  • You are weaker than usual.
  • You have questions or concerns about your condition or care.

When should I seek immediate care or call 911?

  • You cannot move your arm or leg.
  • You have severe pain.
  • You have trouble breathing.

Care Agreement

You have the right to help plan your care. Learn about your health condition and how it may be treated. Discuss treatment options with your healthcare providers to decide what care you want to receive. You always have the right to refuse treatment. The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

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