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What is polymyositis? — Polymyositis (PM) is a condition that causes muscle weakness. In PM, the muscles get inflamed. Doctors don't know what causes PM.
PM is more common in adults, but it can also happen in children.
What are the symptoms of polymyositis? — PM 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 PM can have trouble climbing stairs, lifting things above their head, or swallowing.
Is there a test for polymyositis? — 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.
An imaging test called an MRI scan – Imaging tests create pictures of the inside of the body.
How is polymyositis treated? — The main treatment for PM includes medicines called steroids. Steroids help reduce inflammation. These are not the same as the steroids some athletes take illegally.
People with PM usually need to take steroids for a long time. But steroids have side effects of their own. They can make your bones weak and raise 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 medicines help reduce inflammation, too, but are different than steroids. Sometimes, doctors prescribe both steroids and these other medicines at the same time to treat PM.
In children, long-term use of steroids can slow normal growth. To help prevent this side effect, doctors usually prescribe steroids along with other medicines to children. That way, the children can take less of the steroids and have a better chance of growing normally.
Other treatment for PM 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
Changing what and how you eat, if you have trouble swallowing or choke easily on your food
Taking medicines to help 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 PM under control before you try to 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 PM have only mild symptoms. But many people have more bothersome symptoms that last years.
PM can also cause other types of long-term medical problems. These include lung and heart problems.
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 83085 Version 7.0
Release: 28.2.2 - C28.105
© 2020 UpToDate, Inc. and/or its affiliates. All rights reserved.

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