by EBSCO Medical Review Board


Polymyositis is a rare disease of the muscles. They become inflamed or swollen. This can lead to severe movement problems.

Front Muscles of Trunk
Trunk Core Muscles
Copyright © Nucleus Medical Media, Inc.


This problem may be caused by changes in genes. The changes may cause the immune system to attack muscles.

Risk Factors

Polymyositis is more common in women and people who are 30 to 50 years of age.

The risk of this problem is higher in people who have family members with lupus .


The muscles near the trunk of the body are most affected. Problems may be:

  • Poor muscle strength in the hips, neck, and shoulders
  • Muscle pain that gets worse over time
  • Low energy
  • Using more effort than usual to climb stairs
  • Trouble rising from a chair
  • Problems reaching above the head
  • Having a dry cough that will not go away
  • Problems swallowing

Polymyositis can lead to:


The doctor will ask about your symptoms and health history. A physical exam will be done.

These tests may be done to confirm muscle disease:

  • Blood tests—to look for signs of muscle breakdown
  • Electromyogram (EMG)—test electrical activity of the muscle
  • MRI scan —to look for inflammation
  • Muscle biopsy —to look for inflammation or damage


The disease starts slowly and gets worse over time. There is no cure. The muscles will get weaker and more painful without treatment.

The goal of treatment is to manage symptoms. Choices are:


Some options are:

  • Corticosteroids—to ease inflammation
  • Immunosuppressants—to decrease damage caused by immune system
  • IV immunoglobulin therapy —special proteins that may help the immune system work better

Support Therapy

Muscle weakness can cause a loss of function. Therapy may help. Options are:

  • Physical therapy to help with strength and range of motion
  • Occupational therapy to help with daily tasks and self care
  • Speech therapy to improve swallowing and speech


There are no guidelines to prevent this health problem.


American Autoimmune Related Diseases Association 

The Myositis Association 


The Arthritis Society 

Health Canada 


Diagnosis. The Myositis Association website. Available at: Accessed January 25, 2021.

Idiopathic inflammatory myopathy. EBSCO DynaMed website. Available at: Accessed January 25, 2021.

Milone M. Diagnosis and Management of Immune-Mediated Myopathies. Mayo Clin Proc. 2017 May;92(5):826-837.

Myositis. Ortho Info—American Academy of Orthopaedic Surgeons website. Available at: Accessed January 25, 2021.

Polymyositis information page. National Institute of Neurological Disorders and Stroke website. Available at: Accessed January 25, 2021.

Treatment and disease management. Myositis Association website. Available at: Accessed January 25, 2021.

Types of myositis. Myositis Association website. Available at: Accessed January 25, 2021.

Revision Information

  • Reviewer: EBSCO Medical Review Board Rimas Lukas, MD
  • Review Date: 12/2020
  • Update Date: 01/25/2021