Inclusion-body myositis

Marinos C Dalakas MD (

Dr. Dalakas of the National and Kapodistrian University of Athens Medical School in Greece and Thomas Jefferson University, Philadelphia, Pennsylvania, received honorariums from Baxalta (Shire), Novartis, Pfizer, CSL, and Octapharma for consulting, serving on advisory committees, and speaking engagements.

Emma Ciafaloni MD, editor. (

Dr. Ciafaloni of the University of Rochester received personal compensation for serving on advisory boards and/or as a consultant for Avexis, Biogen, Pfizer, PTC Therapeutics, Sarepta, Ra pharma, Wave, and Strongbridge Biopharma; and for serving on a speaker’s bureau for Biogen. Dr Ciafaloni also received research and/or grant support from Orphazyme, PTC Therapeutics, Santhera, and Sarepta.

Originally released March 23, 1994; last updated January 3, 2020; expires January 3, 2023

This article includes discussion of inclusion body myositis, IBM, inclusion-body myositis, and inclusion body myopathy. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.


Inclusion-body myositis is the most frequent and disabling myopathy seen in patients over 45 to 50 years of age. The distinct clinical features that lead to correct diagnosis and the inclusion-body myositis mimics are highlighted. Inclusion-body myositis has a complex pathogenesis in which autoimmune and inflammatory features coexist with elements of degeneration and abundant accumulations of various stressor proteins. In this article, the author discusses the pitfalls in diagnosis, the diagnostic markers, and the role of inflammation and degeneration in the pathogenesis of the disease, including the interaction between these processes. The latest trends in therapeutic strategies are also presented.

Historical note and terminology

Inclusion-body myositis (IBM) was first recognized as a distinct entity between 1967 and 1971. Three groups identified distinct microtubular filamentous inclusions by electron microscopy in the muscle biopsies of some patients with presumed polymyositis (Chou 1986; Carpenter et al 1970; Yunis and Samaha 1971). The term "inclusion-body myositis" was coined to stress the uniqueness of the disease and separate it from polymyositis (Yunis and Samaha 1971). Carpenter and colleagues' seminal paper emphasizing the clinical entity (Carpenter et al 1978) brought the disease to the surface and stimulated the interest of a number of investigators, including the author of this article.

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