National Center for Advancing and Translational Sciences Genetic and Rare Diseases Information Center, a program of the National Center for Advancing and Translational Sciences

Polymyositis

Polymyositis is a type of inflammatory myopathy, which refers to a group of muscle diseases characterized by chronic muscle inflammation and weakness. The muscles affected by polymyositis are the skeletal muscles (those involved with making movements) on both sides of the body. Although the disease can affect people of all ages, most cases are seen in adults between the ages of 31 and 60 years. The disease is more common among women and among black individuals.[1] 

The exact cause of polymyositis is unknown. The disease shares many characteristics with autoimmune disorders, which occur when the immune system mistakenly attacks healthy body tissues. In some cases, the disease may be associated with viral infections, connective tissue disorders, or an increased risk for malignancies (cancer). Diagnosis is based on a clinical examination that may include laboratory tests, imaging studies, electromyography, and a muscle biopsy.[2] Although there is no cure for polymyositis, treatment with corticosteroids or immunosuppressants can improve muscle strength and function.[1][2]
Last updated: 9/25/2017
Polymyositis is characterized by chronic muscle inflammation and weakness involving the skeletal muscles (those involved with making movements) on both sides of the body.[1] Weakness generally starts in the proximal muscles (those closest to the chest and abdomen, such as muscles of the upper arm and shoulder and the upper leg and hip). The symptoms of polymyositis may continue to worsen from the time the disease presents over a period of weeks or months. The muscle weakness can cause difficulties climbing stairs, rising from a seated position, lifting objects, or reaching overhead.[1] In some cases, the distal muscles (those further away from the chest and abdomen including the lower arms, hands, lower legs, and feet) may also be affected as the disease progresses.[1]  

Other symptoms of polymyositis include arthritis, shortness of breath, difficulty swallowing and speaking, mild joint or muscle tenderness, fatigue, and heart arrhythmias. People with polymyositis may have an increased risk to develop cancer.[1][2] 
Last updated: 9/25/2017
The exact cause of polymyositis is unknown. The disease is thought to be related to problems with the immune system, and the disease shares many similarities with autoimmune diseases. An autoimmune disease occurs when the immune system mistakenly attacks healthy body tissues. It appears that the cells of the muscles (muscle fibers) of individuals with polymyositis are not protected from the body’s immune system. Therefore, the immune system can attack the muscle fibers, which causes them to become damaged, inflamed, and weakened.[2] 

For some people, symptoms of polymyositis may be associated with connective tissue disorders, viral infections such as HIV-AIDS, other autoimmune diseases, or diseases that affect the ability to breathe.[2][3][4] This means that individuals who have any of these diseases are at a higher risk to develop polymyositis.[1][2]
Last updated: 9/25/2017
Changes (mutations) in a specific gene are not known to cause polymyositis.[2] In general, autoimmune diseases are thought to be caused by a combination of genetic and environmental factors. In some cases, multiple people in the same family may be affected by an autoimmune disease. Therefore, it is possible for people with polymyositis to have other family members affected by the disease or by other autoimmune diseases. 
Last updated: 9/25/2017
A diagnosis of polymyositis is often suspected in people with proximal muscle weakness and other signs and symptoms associated with the disease. Additional testing can then be ordered to confirm the diagnosis and rule out other diseases that may cause similar features. The testing may include:[2][5][6]
Last updated: 9/25/2017
The treatment of polymyositis is based on the signs and symptoms present in each person. Although there is currently no cure, symptoms of the disease may be managed with the following:[2][7]
  • Medications such as corticosteroids, corticosteroid-sparing agents, or immunosuppressive drugs
  • Physical therapy to improve muscle strength and flexibility
  • Speech therapy to address difficulties with swallowing and speech
  • Intravenous immunoglobulin: an infusion of healthy antibodies that are given to block damaging autoantibodies that attack the muscle
Mescape Reference offers more specific information regarding the diagnosis and treatment of polymyositis.
Last updated: 9/25/2017
The long-term outlook (prognosis) for people affected by polymyositis varies. Most affected people respond well to treatment and regain muscle strength, although a certain degree of muscle weakness may persist in some cases.[2] In most cases, polymyositis is not life-threatening, and many people recover partially or completely from the disease.[8] People who recover from polymyositis after treatment may be at risk of a recurrence of symptoms.[9]

If the treatment for polymyositis is not effective, affected individuals may develop significant disability.[7] In rare cases, people with severe and progressive muscle weakness may develop respiratory failure or pneumonia. Difficulty swallowing may cause weight loss and malnutrition.[1] Individuals with polymyositis may be more likely to develop other autoimmune diseases, cancer, or osteoporosis.[2]
Last updated: 9/25/2017

Research helps us better understand diseases and can lead to advances in diagnosis and treatment. This section provides resources to help you learn about medical research and ways to get involved.

Clinical Research Resources

  • ClinicalTrials.gov lists trials that are related to Polymyositis. Click on the link to go to ClinicalTrials.gov to read descriptions of these studies.

    Please note: Studies listed on the ClinicalTrials.gov website are listed for informational purposes only; being listed does not reflect an endorsement by GARD or the NIH. We strongly recommend that you talk with a trusted healthcare provider before choosing to participate in any clinical study.
  • The Research Portfolio Online Reporting Tool (RePORT) provides access to reports, data, and analyses of research activities at the National Institutes of Health (NIH), including information on NIH expenditures and the results of NIH-supported research. Although these projects may not conduct studies on humans, you may want to contact the investigators to learn more. To search for studies, enter the disease name in the "Text Search" box. Then click "Submit Query".

Patient Registry

  • The Autoimmune Registry supports research for Polymyositis by collecting information about patients with this and other autoimmune diseases. You can join the registry to share your information with researchers and receive updates about participating in new research studies. Learn more about registries.

Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

Organizations Providing General Support

Living with a genetic or rare disease can impact the daily lives of patients and families. These resources can help families navigate various aspects of living with a rare disease.

Financial Resources

  • The Assistance Fund provides various services, including education and financial aid, to help patients with a chronic or serious illness cover the cost of FDA-approved medications. Patients must be U.S citizens or permanent residents.

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • The Mayo Clinic Web site provides further information on Polymyositis.
  • MedlinePlus was designed by the National Library of Medicine to help you research your health questions, and it provides more information about this topic.
  • The National Institute of Neurological Disorders and Stroke (NINDS) collects and disseminates research information related to neurological disorders. Click on the link to view information on this topic.

In-Depth Information

  • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Polymyositis. Click on the link to view a sample search on this topic.

Questions sent to GARD may be posted here if the information could be helpful to others. We remove all identifying information when posting a question to protect your privacy. If you do not want your question posted, please let us know.

  1. Polymyositis Information Page. National Institute of Neurological Disorders and Stroke (NINDS). 2018; https://www.ninds.nih.gov/Disorders/All-Disorders/Polymyositis-Information-Page.
  2. Pappu R & Seetharaman M. Polymyositis. Medscape Reference. February 12, 2018; http://emedicine.medscape.com/article/335925-overview.
  3. Bhansing KJ, Vonk-Noordegraaf A, Oosterveer FPT, van Riel PLCM, and Vonk MC. Pulmonary arterial hypertension, a novelty in idiopathic inflammatory myopathies: insights and first experiences with vasoactive therapy. RMD Open. 2017; 3(1):https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5574416/.
  4. Svensson J, Holmgvist M, Lundberg IE, and Arkema EV. Infections and respiratory tract disease as risk factors for idiopathic inflammatory myopathies: a population-based case-control study. Annals of the Rheumatic Diseases. August 30, 2017; https://www.ncbi.nlm.nih.gov/pubmed/28855175.
  5. Miller ML. Diagnosis and differential diagnosis of dermatomyositis and polymyositis in adults. UpToDate. September 18, 2016; http://www.uptodate.com/contents/diagnosis-and-differential-diagnosis-of-dermatomyositis-and-polymyositis-in-adults.
  6. Burlina P, Billings S, and Albayda J. Automated diagnosis of myositis from muscle ultrasound: Exploring the use of machine learning and deep learning methods. PLoS One. August 30, 2017; 12(8):http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0184059.
  7. Miller ML. Initial treatment of dermatomyositis and polymyositis in adults. UpToDate. June 13, 2017; http://www.uptodate.com/contents/topic.do?topicKey=RHEUM/5160.
  8. Polymyositis (PM). Muscular Dystrophy Association. https://www.mda.org/disease/polymyositis. Accessed 9/17/2017.
  9. Hajj-ali RA. Polymyositis and Dermatomyositis. Merck Manual. June 2013; http://www.merckmanuals.com/home/bone,-joint,-and-muscle-disorders/autoimmune-disorders-of-connective-tissue/polymyositis-and-dermatomyositis.