Immune-Mediated Necrotizing Myopathy (IMNM)

Medical Management

Though there is no cure for immune-mediated necrotizing myopathy (IMNM), early and intensive treatment with drugs that suppress the immune system (immunosuppressive drugs) can sometimes help to manage the disease and avoid long-term disability.

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 steroid myopathy (weakness from high dose steroids), decreased bone density, increased tissue swelling (edema) and/or weight gain.

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

Treatment plans are typically individualized to meet the needs of the affected person and ongoing monitoring is required to optimize the treatment protocol.

Supportive care

Multidisciplinary care can improve the overall health of people living with IMNM, 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).

References

1. Dalakas MC. Inflammatory Muscle Diseases. Longo DL, ed. N Engl J Med. 2015;372(18):1734-1747. doi:10.1056/NEJMra1402225
2. Pinal-Fernandez I, Casal-Dominguez M, Mammen AL. Immune-Mediated Necrotizing Myopathy. Curr Rheumatol Rep. 2018;20(4):21. doi:10.1007/s11926-018-0732-6
3. Allenbach Y, Guiguet M, Rigolet A, Marie I, Hachulla E, Drouot L, et al. Efficacy of Rituximab in Refractory Inflammatory Myopathies Associated with Anti- Synthetase Auto-Antibodies: An Open-Label, Phase II Trial. PloS One 2015;10:e0133702.
4. Allenbach Y, Mammen AL, Benveniste O, Stenzel W, Immune-Mediated Necrotizing Myopathies Working Group. 224th ENMC International Workshop:: Clinico-sero-pathological classification of immune-mediated necrotizing myopathies Zandvoort, The Netherlands, 14-16 October 2016. Neuromuscul. Disord. NMD 2018;28:87–99.
5. Mammen AL, Tiniakou E. Intravenous Immune Globulin for Statin-Triggered Autoimmune Myopathy. N. Engl. J. Med. 2015;373:1680–2.

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