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  • Updated 02.28.2024
  • Released 03.11.1994
  • Expires For CME 02.28.2027

Polymyositis, necrotizing autoimmune myositis, overlap-myositis, and myofasciitis


Historical note and terminology

Polymyositis: a historical perspective. Although first recorded by Wagner in 1863 (151), polymyositis became a recognized clinical entity 75 years later when Walton and Adams published a remarkable monograph titled Polymyositis (152). These authors defined the term “polymyositis” as an all-inclusive designation of a group of myopathies characterized by a single basic disease process related to "other collagen" diseases or arising as the result of "hypersensitivity response to allergic inflammation." Polymyositis is a rare disorder that for years, by all accounts, has been the most overdiagnosed acquired myopathy. Although it is unclear whether it exists as a distinct entity, it is discussed not only for historical reasons but also because it is still diagnosed by various practitioners. Although this author believes that it does not exist as a single entity, the evolution and now almost extinction of polymyositis, considered 3 to 4 decades ago as the most common autoimmune inflammatory myositis, has taught us a lot about muscle immunopathology and, specifically, T cell–mediated myocytotoxicity. Therefore, it is discussed here as “myositis” as it is not even included in some new classifications of autoimmune inflammatory myopathies. Further, it is important to include it in the context of two similar but now distinct and more frequent entities that have evolved over the last two decades, namely necrotizing autoimmune myositis and overlap myositis, because both, along with inclusion body myositis, have been misdiagnosed as polymyositis for years.

The study of polymyositis (now referred to as myositis) when all the other types of myositis have been excluded requires a scholarly review of the neurologic examination, muscle histopathology, immunopathology, and biochemistry to ensure that toxic, metabolic, or mitochondrial muscle diseases are not missed and that the other four entities—inclusion body myositis, dermatomyositis, necrotizing autoimmune myositis, and overlap myositis—have been excluded (12; 74; 29; 30; 36; 37; 39; 46; 47; 49; 59; 133; 40; 116; 46; 46). This form of myositis is usually seen in connection without autoimmune or connective tissue diseases.

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