Myositis is inflammation of the muscle and polymyositis denotes that that inflammation affects not one, but many muscles.

Polymyositis is a fairly uncommon condition that leads to increasing weakness of the skeletal muscles (those muscles involved in movement) and it can affect the body bilaterally (on both sides).

People with this inflammatory disease usually find it difficult to do basic everyday maneuvers such as rising from a seated position, climbing stairs or lifting objects overhead.

The Myositis Association, Patient stories, Polymyositis

Polymyositis is characterized by:

  • Progressive muscle weakness that usually starts in those muscles closest to the body’s trunk (i.e. proximal muscles).
  • Difficulty in swallowing and speaking (dysphagia and dysarthria, respectively)
  • Shortness of breath
  • Heart beat irregularities
  • Arthritis

In some cases as the disease progresses, the muscles that are furthest away from the trunk of the body (i.e. distal muscles), such as those in the forearms and ankles, may become affected. Furthermore, patients may have other symptoms including but not limited to a low-grade fever and peripheral adenopathy (enlargement of lymph nodes).


The cause of polymyositis has not been identified yet. However, it is speculated that it may be linked to viral agents and autoimmune factors.

Cytotoxic T cells with an unknown autoantigen mediate the inflammatory process seen in the muscles of patients with polymyositis. It is also believed that cancer may be a potential trigger for the condition through an immune pathway that involves attacking the cancer cells as well as the muscles.

Polymyositis is most commonly seen to affect adults between their third and fifth decades of life. Moreover, it is more prevalent women as opposed to men and in blacks than in white.

Associated Conditions

Associated conditions include infectious diseases, such as HIV-AIDS and collagen-vascular or autoimmune disorders (e.g. lupus). Polymyositis and its other associated muscles diseases tend to increase the risk of developing cancer.

Factors that contribute to this increase incidence of cancer include:

  • Male sex
  • Older age
  • Cutaneous necrosis
  • Vasculitis
  • Elevated inflammatory markers in blood such as ESR, CRP and CK.

Arthritis and Raynaud’s syndrome are also contributing factors that increase one’s chance of developing a malignancy.  The specific malignancies associated with polymyositis are lung cancer, nasopharyngeal cancer and non-Hodgkins lymphoma.

Treatment and prognosis

Polymyositis has no cure. However, there are several available treatment options for the symptoms. These are not just limited to pharmacotherapy, but include physical and heat therapy as well as exercise and the use of assistive devices. The homestay of treatment for polymyositis is systemic corticosteroid drugs such as prednisolone.

Immunosuppressive agents, for example methotrexate, may also be used to reduce inflammation. Intravenous immunoglobulins have also been used to help alleviate the symptoms. Heat therapy involves the use of ultrasound and microwaves, while physical therapy is generally recommended to avoid muscles wasting away due to inactivity.

Most patients tend to respond very well to the current therapies used; however, response varies across the board and those with severe disease presentation have a bad prognosis. Although rare, patients with severe disease may develop pneumonia and respiratory failure.

Therapy aims at improving muscle strength and function and thereby enabling a good quality of life. Current research being done on polymyositis is exploring the possibility of targeting gene expression and is also looking into the role of viral infection in the development of the condition.

Further Reading

Last Updated: Feb 27, 2019

Dr. Damien Jonas Wilson

Written by

Dr. Damien Jonas Wilson

Dr. Damien Jonas Wilson is a medical doctor from St. Martin in the Caribbean. He was awarded his Medical Degree (MD) from the University of Zagreb Teaching Hospital. His training in general medicine and surgery compliments his degree in biomolecular engineering (BASc.Eng.) from Utrecht, the Netherlands. During this degree, he completed a dissertation in the field of oncology at the Harvard Medical School/ Massachusetts General Hospital. Dr. Wilson currently works in the UK as a medical practitioner.


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  1. Sandile Siko Sandile Siko South Africa says:

    Hi, Polymiositis is a very rare desease as indicated on the article... are there any statistics on the number of people who may currently be having this desease.. what kind of support shoild be offered to partners affected by this desease

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
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