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, Octapharma, and Therapath for consulting, serving on advisory committees, and speaking engagements.

Emma Ciafaloni MD, editor. (

Dr. Ciafaloni of the University of Rochester received consulting fees from Biogen and Pfeizer and research grants from Sarepta and Santhera.

Originally released March 23, 1994; last updated June 5, 2018; expires June 5, 2021


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 50 years of age. The distinct clinical features that lead to correct diagnosis and 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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