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Dermatomyositis (DM)


What is dermatomyositis? — Dermatomyositis (DM) is a condition that causes muscle weakness and skin rashes. In DM, the muscles and skin get inflamed. A small number of people also develop lung problems. Doctors don't know what causes DM.
DM is more common in adults, but it can also happen in children.
What are the symptoms of dermatomyositis? — DM causes:
Muscle weakness – The weakness affects both sides of the body and usually happens slowly over time. It involves muscles closest to the trunk of the body, such as those in the neck, shoulders, hips, and thighs. Depending on the muscles involved, people with DM can have trouble climbing stairs, lifting things overhead, or swallowing.
Skin rashes – DM causes different kinds of skin rashes on different parts of the body. The rashes are red, sometimes scaly, and usually very itchy. Sunlight usually makes the rashes worse. People can get rashes on their:
•Fingers, including on the backs of the finger joints and around the finger nails
•Elbows and knees
•Upper eyelids
•Neck, upper chest, or upper back
Interstitial lung disease – About 1 in 10 people with DM develop interstitial lung disease. Interstitial lung disease can cause inflammation and sometimes scarring in the lungs. This makes it hard for oxygen to get from the air into the lungs, which can make it hard to breathe.
Is there a test for dermatomyositis? — Yes. Your doctor or nurse will order one or more of the following tests:
Blood tests
Electromyography, or "EMG" – This test shows whether your muscles are responding to the nerves' electrical signals in the correct way.
Muscle biopsy – For this test, the doctor takes a small sample of tissue from a muscle that is weak. Then another doctor looks at the sample under a microscope.
Skin biopsy – For this test, the doctor takes a small sample of skin from your skin rash. Then another doctor looks at the sample under a microscope.
An imaging test called an MRI scan – Imaging tests create pictures of the inside of the body.
How is dermatomyositis treated? — Treatment for DM involves different parts.
The main treatment for DM includes medicines called steroids. Steroids help reduce inflammation. These are not the same as the steroids some athletes take illegally.
People with DM usually need to take steroids for a long time. But steroids have side effects of their own. They can make your bones weak and increase your chances of getting an infection. To avoid these side effects as much as possible, your doctor will slowly lower (or "taper") your dose over time.
If you can't take steroids, the steroids don't help enough, or your symptoms come back, your doctor can treat you with other medicines. These include medicines that calm your immune (infection-fighting) system.
Your doctor will also give you medicines to help your skin symptoms and itching. Some of these medicines go on the skin. Others come as a pill.
Other treatment for DM involves keeping your body as strong as possible and preventing further problems. This usually includes:
Working with a physical therapist (exercise expert) to learn exercises to strengthen your muscles
Avoiding sunlight by wearing sunscreen, a wide-brimmed hat, long-sleeved shirt, and long pants
Changing what and how you eat, if you have trouble swallowing or choke easily on your food
Taking medicines to prevent side effects from the steroids
What if I want to get pregnant? — If you want to get pregnant, talk with your doctor or nurse. He or she will work with you to get your DM under control before you get pregnant. Plus, he or she will make sure your medicines are safe to take during pregnancy.
What will my life be like? — It depends on your individual situation. Some people with DM have only mild symptoms. But many people have more bothersome symptoms that last years.
DM can be associated with certain types of cancer in adults. Your doctor may recommend certain tests. Your doctor may also do additional testing to make sure you don't have heart problems caused by DM.
All topics are updated as new evidence becomes available and our peer review process is complete.
This topic retrieved from UpToDate on: Mar 30, 2020.
Topic 82977 Version 8.0
Release: 28.2.2 - C28.105
© 2020 UpToDate, Inc. and/or its affiliates. All rights reserved.

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