Polymyositis (PM)

Medical Management

Polymyositis (PM) is a highly treatable disease. Drugs that suppress the immune system (immunosuppressive drugs) are the mainstay of therapy.

Immunosuppressive therapy

Glucocorticoids, particularly prednisone, are often the first-line treatment. These medications help to reduce inflammation and swelling, and suppress damaging autoimmune responses. Long-term use of high-dose glucocorticoid therapy, however, may produce unwanted side effects, such as decreased bone density, increased tissue swelling (edema) and/or weight gain.

For some affected people, therapy with other immunosuppressive drugs, such as azathioprine, methotrexate, mycophenoloate mofetil, tacrolimus, or cyclosporine may be beneficial. Additional treatment options used in combination may include the monoclonal antibody rituximab or intravenous immunoglobulin (IVIG).

Treatment plans are typically individualized to meet the needs of the affected person and ongoing monitoring is required to optimize the treatment protocol. In some cases, affected people may require prolonged maintenance therapy throughout their lives, while in others, therapy may be gradually withdrawn as symptoms resolve. Some people recover completely, while others experience greatly diminished symptoms for long periods of time. Several years of treatment to suppress the immune system may be necessary to achieve these results.

Supportive care

Multidisciplinary care can improve the overall health of people living with PM, and may include recommendations from a variety of specialists. Physical therapy may be recommended to help improve muscle strength and avoid development of contractures (muscle shortening/tightening). Supportive treatment can help manage complications such as swallowing or breathing difficulties or abnormalities of the heart, lungs, or gastrointestinal tract. In people with associated malignancy, removal of the cancer may be required.

References

1. Findlay AR, Goyal NA, Mozaffar T. An overview of polymyositis and dermatomyositis. Muscle Nerve. 2015;51(5):638-656. doi:10.1002/MUS.24566
2. Baig S, Paik JJ. Inflammatory muscle disease – An update. Best Pract Res Clin Rheumatol. 2020;34(1):101484. doi:10.1016/j.berh.2019.101484

Last update: Feb 2023
Reviewed by Julie Paik, MD, MHS; Johns Hopkins University