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Polymyositis is one of a group of rare diseases called the inflammatory myopathies that involve chronic (long-standing) muscle inflammation and weakness, and in some cases, pain. Myopathy is a general term used to describe a number of conditions affecting the muscles. All myopathies can cause muscle weakness. Both children and adults can be affected.

Polymyositis affects skeletal muscles (the type involved in body movement) on both sides of the body. It is rarely seen in people younger than age 20. Generally, the onset occurs between age 30 and 60. Untreated progressive muscle weakness may lead to difficulty doing the following actions:

  • Swallowing
  • Speaking
  • Rising from a sitting position
  • Climbing stairs
  • Lifting objects
  • Reaching overhead

Some people with polymyositis also may develop:

  • Arthritis
  • Shortness of breath
  • Heart arrhythmias (irregular heartbeats)
  • Congestive heart failure (when the heart is no longer able to pump out enough oxygen-rich blood)

In some cases of polymyositis, the distal muscles, which are the muscles away from the center of the body, such as those in the forearms and around the ankles and wrists, may be affected as the disease progresses. The disorder also may be associated with collagen-vascular or autoimmune diseases such as lupus, in which the body's immune response system that normally defends against infection and disease attacks its own muscle fibers, blood vessels, connective tissue, organs, or joints.

How can I or my loved one help improve care for people with polymyositis?

Consider participating in a clinical trial so clinicians and scientists can learn more about polymyositis and related disorders. Clinical research uses human volunteers to help researchers learn more about a disorder and perhaps find better ways to safely detect, treat, or prevent disease.

All types of volunteers are needed—those who are healthy or may have an illness or disease—of all different ages, sexes, races, and ethnicities to ensure that study results apply to as many people as possible, and that treatments will be safe and effective for everyone who will use them.

For information about participating in clinical research visit NIH Clinical Research Trials and You. Learn about clinical trials currently looking for people with polymyositis at

Where can I find more information about polymyositis?

The following organizations offer resources that help individuals, families, friends, and caregivers of people living with myopathy and muscle diseases:

Autoimmune Association
Phone: 586-776-3900

Muscular Dystrophy Association

Myositis Association

Content source: Accessed June 29, 2023.

The information in this document is for general educational purposes only. It is not intended to substitute for personalized professional advice. Although the information was obtained from sources believed to be reliable, MedLink, its representatives, and the providers of the information do not guarantee its accuracy and disclaim responsibility for adverse consequences resulting from its use. For further information, consult a physician and the organization referred to herein.

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