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The National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), a component of the National Institutes of Health (NIH), is a leading federal funder of research on muscle diseases like polymyositis.

What is polymyositis?

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.

Learn About Clinical Trials
Clinical trials are studies that allow us to learn more about disorders and improve care. They can help connect patients with new and upcoming treatment options.

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 Clinicaltrials.gov.

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

Muscular Dystrophy Association

Myositis Association

Order publications from the NINDS Catalog
The NINDS Publication Catalog offers printed materials on neurological disorders for patients, health professionals, and the general public. All materials are free of charge, and a downloadable PDF version is also available for most publications.