Triggers of inflammatory myopathy: insights into pathogenesis

The inflammatory myopathies, which include dermatomyositis, polymyositis, and the immune-mediated necrotizing myopathies, are a heterogeneous group of autoimmune diseases that manifest with muscle, skin, or lung damage. Collectively, these autoimmune diseases result from loss of tolerance to a select group of self-antigens, although the precise mechanism through which this occurs is not known. Infection, malignancy, and certain medications including statins and the immune checkpoint inhibitors used in cancer therapy have been identified as potential immunologic triggers of the inflammatory myopathies. Some of these triggers are classically associated with specific myositis-specific autoantibodies (MSAs). The strong association between certain triggers and MSAs provides insights into how an immunologic event can lead to loss of tolerance to specific self-antigens, resulting in autoimmune disease. In this review, we discuss the proposed triggers of the inflammatory myopathies and their associations with MSAs, and provide insights into how these triggers may result in the inflammatory myopathies.